Exacty the same problem here. When pressing play (in Logic x), Mine can be as bad as 10 seconds. VE Pro 5 didn't behave like that at all.
When I press stop twice on Logic (i.e. return to zero) then press play. each instance displays 'Engine Stopped' for a split second then 'Engine started'. If somehow Logic is stopping the engine on all VE Pro instances and then re-starting them then it's not suprising of such a massive delays. At first I thought this was an autosave setting but doesn't seem to be. I've looket at the "start/stop engine' and 'start / stop transport' under the Transport menu but doesn't seem to make a difference. I also thought it could be a MIDI reset message in Logic (upon stop) but only have mod, sustain and pitch bend reset messages active.
Sadly this is completely unusable for me, hoping VE Pro 5 will still install OK
RJ
(Logic Pro X 10.2.4, Mac Pro 2013 64gb, OSX 10.10.5, 61 instances within VE Pro)