Strange men. I have a macpro 8core 2.8ghz/10.5.6/Logic 8.0.2 and I use a shitload of outboard gear.
I use a projectmix I/O with a Digimax FS (adat connected) And I have like 2 stereo reverbs, LA2A and 1176 from AU and a G-masterbuss clone. All patch and ready to go in logic (maked a template in logic). And I have never had this kind of problems

. Even with Parr/comp with the drum buss and the G-comp and then putting them back together in a new bus. Mhz perhaps there is a latency of what... under 10samples... I don't see / hear that anymore.
BTW I HAVE to say that. YES you must put always a i/o plugin on the buss that you sending out a signal and on the one that you receiving you treated signal.... Its abit fugged up in logic but hell it works.
BTW are you sure that you put in the options the I/O safety bumper on, Process Buffer Ranger: High, Recording delay @ 1Ms... (so your sure that the signal before recording is send properly). I/O buffer size to 32ms>?
And in "generel" tab in audio. Compensation set to ALL + Low latencymode plus the limit to 1ms (same as recording delay).
I have this setting and it works 99 out of 100