Exactly same here - found this in /var/log/system that describes the issue (IP's redacted)
Mar 23 08:14:43 Dragunov nesessionmanager[417]: NESMLegacySession[89684807-78F0-4703-AFCC-9BC59DD46665]: Received a start command from SystemUIServer[288]
Mar 23 08:14:43 Dragunov nesessionmanager[417]: NESMLegacySession[89684807-78F0-4703-AFCC-9BC59DD46665]: status changed to connecting
Mar 23 08:14:43 Dragunov nesessionmanager[417]: IPSec connecting to server X.X.X.X
Mar 23 08:14:43 Dragunov nesessionmanager[417]: IPSec Phase1 starting.
Mar 23 08:14:43 Dragunov racoon[236]: accepted connection on vpn control socket.
Mar 23 08:14:43 --- last message repeated 1 time ---
Mar 23 08:14:43 Dragunov racoon[236]: IPSec connecting to server X.X.X.X
Mar 23 08:14:43 --- last message repeated 1 time ---
Mar 23 08:14:43 Dragunov racoon[236]: Connecting.
Mar 23 08:14:43 Dragunov racoon[236]: IPSec Phase 1 started (Initiated by me).
Mar 23 08:14:43 --- last message repeated 1 time ---
Mar 23 08:14:43 Dragunov racoon[236]: IKE Packet: transmit success. (Initiator, Main-Mode message 1).
Mar 23 08:14:43 Dragunov racoon[236]: >>>>> phase change status = Phase 1 started by us
Mar 23 08:14:43 --- last message repeated 1 time ---
Mar 23 08:14:43 Dragunov racoon[236]: none message must be encrypted, status 0x1461, side 0
Mar 23 08:14:46 --- last message repeated 1 time ---
Mar 23 08:14:46 Dragunov racoon[236]: IKE Packet: transmit success. (Phase 1 Retransmit).
Mar 23 08:14:46 Dragunov racoon[236]: none message must be encrypted, status 0x1461, side 0
Mar 23 08:14:49 --- last message repeated 1 time ---
Mar 23 08:14:49 Dragunov racoon[236]: IKE Packet: transmit success. (Phase 1 Retransmit).
Mar 23 08:14:49 Dragunov racoon[236]: none message must be encrypted, status 0x1461, side 0
Mar 23 08:14:52 --- last message repeated 1 time ---
Mar 23 08:14:52 Dragunov racoon[236]: IKE Packet: transmit success. (Phase 1 Retransmit).
Mar 23 08:14:52 Dragunov racoon[236]: none message must be encrypted, status 0x1461, side 0
Mar 23 08:14:53 --- last message repeated 1 time ---
Mar 23 08:14:53 Dragunov nesessionmanager[417]: NESMLegacySession[:89684807-78F0-4703-AFCC-9BC59DD46665]: status changed to disconnecting
Mar 23 08:14:53 Dragunov nesessionmanager[417]: IPSec disconnecting from server X.X.X.X
Mar 23 08:14:53 Dragunov racoon[236]: IPSec disconnecting from server X.X.X.X
Mar 23 08:14:53 --- last message repeated 3 times ---
Mar 23 08:14:53 Dragunov nesessionmanager[417]: NESMLegacySession[89684807-78F0-4703-AFCC-9BC59DD46665]: status changed to disconnected, last stop reason None
In addition I updated the iOS install on my iPhone 6 - and the exact same vpn with the exact config still works on my iPhone - so it's just OS X 10.11.4 affected.