I really don't understand why people uninstall and reinstall Logic Pro for such issues.. It's usually a complete waste of time .. and wont fix anything of this nature.
But anyhow...
If you have a Mac with more than 8 Cores.. set the max number of cores to 8 in Logic's preferences.. Do not set it to Automatic or more than 8. Restart your Mac and see if that fixes this latency...
Note: FWIW.. I have several different testbed Mac Pro's, iMacs, Mac Minis and MBPs here now.. and all of them run 10.10.5 and 10.2 without any latency issues.... I don't know if that's because I am using Motu interfaces exclusively or if it it how i set these rigs up (Other than the Core settings I have done nothing unusual.. that i am aware of ) but I suspect in most cases, as has been proven in the past.. such issues tend to be specific to certain computers... and audio/midi hardware configurations or simply User error.....
Typically other causes are... the use of illegal 3rd party plugins.. or other software installed on the Mac that affects performance.. or conflicts with Logic Pro X (such as Audio Routers like jack and SoundFlower) or the use of troublesome cheaper audio (M-Audio/Avid/Digidesign/Mackie etc) whos drivers are known to be flaky to say the least at times....and/or really cheap midi interfaces and so on.....
You may want to try running Etrecheck...
http://www.etresoft.com/etrecheck
...and study the report it generates to see if there is anything there that could be tha cause of your issues.. If you need help with that, simply post up the report here.... and Ill take a look/see for you.
Cheers..
Nigel
