I reinstalled OS X just as you recommended. It seems that the error message concerning the Recovery set changed:
25/04/15 16:17:52,246 storedownloadd[491]: DownloadServiceDelegate: Accepting new connection <NSXPCConnection: 0x7ff598500fa0> connection from pid 487 with interface <DownloadServiceInterface: 0x7ff598506b50> (PID 487)
25/04/15 16:17:59,751 com.apple.backupd[403]: Starting automatic backup
25/04/15 16:17:59,995 com.apple.backupd[403]: Backing up to /dev/disk2s2: /Volumes/Backup2/Backups.backupdb
25/04/15 16:18:00,806 com.apple.backupd[403]: Event store UUIDs don't match for volume: SSD Boot
25/04/15 16:18:01,454 com.apple.backupd[403]: Deep event scan at path:/ reason:must scan subdirs|new event db|
25/04/15 16:18:01,455 com.apple.backupd[403]: Running event scan
25/04/15 16:18:30,853 mdworker[532]: code validation failed in the process of getting signing information: Error Domain=NSOSStatusErrorDomain Code=-67062 "The operation couldn’t be completed. (OSStatus error -67062.)"
25/04/15 16:18:30,983 mdworker[532]: code validation failed in the process of getting signing information: Error Domain=NSOSStatusErrorDomain Code=-67062 "The operation couldn’t be completed. (OSStatus error -67062.)"
25/04/15 16:18:32,812 com.apple.xpc.launchd[1]: (com.apple.imdmessageservices.IMDMessageServicesAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:18:32,812 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:18:50,000 kernel[0]: process MacsFanControl[451] caught causing excessive wakeups. Observed wakeups rate (per sec): 641; Maximum permitted wakeups rate (per sec): 150; Observation period: 300 seconds; Task lifetime number of wakeups: 45544
25/04/15 16:18:50,539 com.apple.xpc.launchd[1]: (com.apple.ReportCrash[559]) Endpoint has been activated through legacy launch(3) APIs. Please switch to XPC or bootstrap_check_in(): com.apple.ReportCrash
25/04/15 16:18:50,540 ReportCrash[559]: Invoking spindump for pid=451 wakeups_rate=641 duration=71 because of excessive wakeups
25/04/15 16:18:53,089 spindump[560]: Saved wakeups_resource.diag report for MacsFanControl version 1.2.1.0 (???) to /Library/Logs/DiagnosticReports/MacsFanControl_2015-04-25-161853_iMac-van-Hans. wakeups_resource.diag
25/04/15 16:19:18,278 com.apple.backupd[403]: Finished scan
25/04/15 16:19:18,770 com.apple.backupd[403]: Saved event cache at /Volumes/Backup2/Backups.backupdb/iMac van Hans/2015-04-25-161800.inProgress/C8A10FE4-5356-4E21-81A5-6E3F9C14FF93/.F999C86 6-1B71-3466-8990-9540C593C08A.eventdb
25/04/15 16:19:18,868 com.apple.backupd[403]: Not using file event preflight for SSD Boot
25/04/15 16:20:22,939 com.apple.backupd[403]: Will copy (769 bytes) from USERS1
25/04/15 16:20:22,950 com.apple.backupd[403]: Found 423386 files (11,49 GB) needing backup
25/04/15 16:20:23,207 com.apple.backupd[403]: 19,66 GB required (including padding), 1,41 TB available
25/04/15 16:20:50,187 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:20:51,554 cloudphotosd[663]: Unable to register with launch services, result = -10819
25/04/15 16:20:51,588 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:20:54,027 cloudphotosd[663]: +[CSLogger preferencesChanged:] reconfiguring logging
25/04/15 16:20:54,244 cloudphotosd[663]: Determine service transition start: service=com.apple.photo.icloud.myphotostream personId=1353114644 lastKnownPersonId=(null) targetState=-1
25/04/15 16:20:54,244 cloudphotosd[663]: Determine service transition end: 2, currentState: 3, shouldEnableService: 0
25/04/15 16:20:54,566 cloudphotosd[663]: Determine service transition start: service=com.apple.photo.icloud.sharedstreams personId=1353114644 lastKnownPersonId=(null) targetState=-1
25/04/15 16:20:54,566 cloudphotosd[663]: Determine service transition end: 2, currentState: 3, shouldEnableService: 0
25/04/15 16:20:55,464 cloudphotosd[663]: Determine service transition start: service=com.apple.photo.icloud.cloudphoto personId=1353114644 lastKnownPersonId=(null) targetState=0
25/04/15 16:20:55,464 cloudphotosd[663]: Determine service transition end: 2, currentState: 3, shouldEnableService: 0
25/04/15 16:20:56,548 cloudphotosd[663]: New connection request from 666
25/04/15 16:20:57,767 com.apple.photomoments[672]: Photomoments process awakened.
25/04/15 16:20:57,956 com.apple.photomoments[672]: Connection error while checking Apple Internalness. Error: Error Domain=NSCocoaErrorDomain Code=4099 "Couldn’t communicate with a helper application." (The connection to service named com.apple.CrashReporterSupportHelper was invalidated.) UserInfo=0x7f92a143c050 {NSDebugDescription=The connection to service named com.apple.CrashReporterSupportHelper was invalidated.}
25/04/15 16:20:58,164 sandboxd[323]: ([672]) com.apple.photom(672) deny mach-lookup com.apple.CrashReporterSupportHelper
25/04/15 16:20:58,000 kernel[0]: process backupd[403] thread 9125 caught burning CPU! It used more than 50% CPU (Actual recent usage: 50%) over 180 seconds. thread lifetime cpu usage 90.873877 seconds, (42.019109 user, 48.854768 system) ledger info: balance: 90016080142 credit: 90016080142 debit: 0 limit: 90000000000 (50%) period: 180000000000 time since last refill (ns): 179260947065
25/04/15 16:20:58,968 com.apple.xpc.launchd[1]: (com.apple.ReportCrash.Root[677]) Endpoint has been activated through legacy launch(3) APIs. Please switch to XPC or bootstrap_check_in(): com.apple.ReportCrash.DirectoryService
25/04/15 16:20:59,150 com.apple.geod[675]: Connection error while checking Apple Internalness. Error: Error Domain=NSCocoaErrorDomain Code=4099 "Couldn’t communicate with a helper application." (The connection to service named com.apple.CrashReporterSupportHelper was invalidated.) UserInfo=0x7f90e9700130 {NSDebugDescription=The connection to service named com.apple.CrashReporterSupportHelper was invalidated.}
25/04/15 16:20:59,160 sandboxd[323]: ([675]) com.apple.geod(675) deny mach-lookup com.apple.CrashReporterSupportHelper
25/04/15 16:20:59,367 spindump[560]: Saved cpu_resource.diag report for backupd version ??? (???) to /Library/Logs/DiagnosticReports/backupd_2015-04-25-162059_iMac-van-Hans.cpu_res ource.diag
25/04/15 16:21:56,492 mdworker[738]: code validation failed in the process of getting signing information: Error Domain=NSOSStatusErrorDomain Code=-67062 "The operation couldn’t be completed. (OSStatus error -67062.)"
25/04/15 16:21:56,620 mdworker[738]: code validation failed in the process of getting signing information: Error Domain=NSOSStatusErrorDomain Code=-67062 "The operation couldn’t be completed. (OSStatus error -67062.)"
25/04/15 16:23:29,049 com.apple.backupd-helper[68]: Not starting scheduled Time Machine backup: Backup already running
25/04/15 16:23:39,154 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:23:39,795 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:29:15,765 com.apple.xpc.launchd[1]: (com.apple.DataDetectorsDynamicData) The JoinExistingSession key is only available to Application services.
25/04/15 16:29:15,766 com.apple.xpc.launchd[1]: (com.apple.appkit.xpc.sandboxedServiceRunner) The JoinExistingSession key is only available to Application services.
25/04/15 16:29:31,510 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:29:35,483 mdworker[293]: SCNetworkReachability server not available
25/04/15 16:29:35,484 mdworker[293]: SCNetworkReachability server not available
25/04/15 16:29:35,487 mdworker[293]: bootstrap_look_up2 failed with 0x44c
25/04/15 16:29:35,487 mdworker[293]: IOPMConnectionCreate failed, 0xe00002c9
25/04/15 16:29:35,719 sandboxd[323]: ([293]) mdworker(293) deny mach-lookup com.apple.SystemConfiguration.SCNetworkReachability (import fstype:hfs fsflag:480D000 flags:5E diag:0 isXCode:0 uti:public.html plugin:/Library/Spotlight/RichText.mdimporter - find suspect file using: sudo mdutil -t 2310261)
25/04/15 16:29:35,754 sandboxd[323]: ([293]) mdworker(293) deny mach-lookup com.apple.PowerManagement.control (import fstype:hfs fsflag:480D000 flags:5E diag:0 isXCode:0 uti:public.html plugin:/Library/Spotlight/RichText.mdimporter - find suspect file using: sudo mdutil -t 2310261)
25/04/15 16:31:03,369 com.apple.backupd[403]: Copied 223515 items (1,65 GB) from volume SSD Boot. Linked 210906.
25/04/15 16:31:32,355 com.apple.backupd[403]: Copied 14 items (861 bytes) from volume USERS1. Linked 119.
25/04/15 16:31:35,323 com.apple.backupd[403]: Created new backup: 2015-04-25-163135
25/04/15 16:31:35,517 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
25/04/15 16:31:35,000 kernel[0]: hfs: mounted Recovery HD on device disk0s3
25/04/15 16:31:35,871 mds[57]: (Volume.Normal:2464) volume:0x7fb9c213e000 ********** Bootstrapped Creating a default store:0 SpotLoc:(null) SpotVerLoc:(null) occlude:0 /Volumes/Recovery HD
25/04/15 16:31:35,918 fseventsd[44]: Logging disabled completely for device:1: /Volumes/Recovery HD
25/04/15 16:31:35,932 com.apple.backupd[403]: Copying OS X Recovery set
25/04/15 16:31:59,320 mdworker[290]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,320 mdworker[292]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,322 mdworker[293]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,328 mdworker[291]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,330 mdworker[885]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,334 mdworker[294]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,334 mdworker[295]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,335 mdworker[296]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,337 mdworker[297]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,337 mdworker[530]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,339 mdworker[788]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,339 mdworker[327]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,340 mdworker32[1077]: (ImportBailout.Error:1325) Asked to exit for Diskarb
25/04/15 16:31:59,000 kernel[0]: hfs: unmount initiated on Recovery HD on device disk0s3
25/04/15 16:32:00,119 com.apple.backupd[403]: Starting post-backup thinning
25/04/15 16:32:00,120 com.apple.backupd[403]: No post-backup thinning needed: no expired backups exist
25/04/15 16:32:00,133 com.apple.backupd[403]: Backup completed successfully.
25/04/15 16:32:44,591 WindowServer[181]: CGXGetConnectionProperty: Invalid connection 54279
Am I wrong or is the recovery set still " under fire"?