Ok i've got what you mean, while there are no issues with delay compensation if you put the audio in directly on the channel and then return back on an instrument, there are lot of problems if you want to use VEP like an effect using a bus and aux like you did on your video, by the way i've found a workaround to keep the sync but there are some rules to keep in mind and require the use of Voxengo Latency delay (free)
Basically it's not possible to come out from a channel and keep the dry signal in sync with its return from Audio routings in VEP, no chances, at least i've found no ways when you include busses and auxes on the chain.
I've found a way to let it work, let's say i want to create an FX Rack instance in VEP using 4 fx.
My logic is with 1024 samples buffer, if you want to replicate this use the same buffer, you'll be able to lower it later.
1-Create a 5 channel mixer istance in VEP server like the image below
https://postimg.org/image/e5xqer2nh/
you are going to use 10 in and 10 out on the same istance, assigning like the image. The first channel will be the DRY return and the others are the 4 effect i want to use.
2 -create a multitimbral instrument in logic and create 5 auxes, i'll use aux 1-5 and bus1-5 where aux1 and bus1 will be the DRY return, see image.
Assign FXRACK Istance to The multitimbral and add 4 more channels, set 1 buffer, put the I/O only on the first channel instrument.
https://postimg.org/image/ppnop4wsp/
On the auxes Put I/O on every channel and assign VEP audio input sequentially 1-2, 3-4 5-6 and so on..
Now create a normal instrument channel, i'm going to use exs24 and a kick like you did in your video, now the tricky part. if you don't need to use fx from VEP just leave it as is so "stereo out" as output.
In order to use fx from VEP the out will become bus1, assign bus2-3-4-5 on busses in order to send audio to fx in vep. Basically also the dry signal will go throu VEP, this is the only way i've found for now to keep things as easier as possible.
Everything will play out of sync compared to logic's metronome, and here comes voxengo latency delay to help us. insert it on the kick channel and give it the value using this formula (VEP FXRACK instance delay + (logic buffer*2)), in this case will be 2048 + (1024*2) = 4096
https://postimg.org/image/f94496nz1/
everything will play pefectly now :)
If you insert latency inducing plug-in on any logic channel the sync will be kept, at least i've found no issues, you do not have to handle it. there's only 1 rule, THE DRY CHANNEL RETURN MUST BE FLAT, NO PLUG-INS, in my example is bus1 aux1 in1-2/out1-2 from VEP (named aux2 in screenshot sorry). Don't know why honestly but it looks that latency compensation is managed fine on the other multitimbral returns while it does not work if you insert stuff on the first one.
Instead if you insert latency plug-ins in VEP you have to check the latency in FXRACK and adjust voxengo using the formula above (latency + 2048 in my case)
The nice thing you can even route an instrument from vep to itself, basically you just have to add voxengo and out to bus1, like you just did on the exs24 channel, so it works for instruments coming from vep pro too.
This is a bit tricky but also once you get used i think it's not too bad, there are some cases where it could be useful, for example if you want to group some loops and use a compressor in VEP or an heavy fx chain that logic can't handle, but for the majority of the times i think i'll just avoid using bus and auxes in conjunction with VEP audio in, with no bus it works just fine and you can also manage dry/wet using vep mixer (make 2 bus with same input and same output and keep the first one flat).
EDIT: the (easier) alternative method i've just said is like the image below, audio in directly on the instrument, then return back to vep plug-in, same issue here the return channel must be kept flat, if you need to insert stuff just out to a bus and insert plgs on the aux. it looks it handles also latency added by fx inserted in VEP if you respect the flat rule above :)
https://postimg.org/image/ol1c1u7eb/
any improvement is welcome :)