Here's what was odd:
1) Vampires phasing in and out at light speed.
They're not even targetable in the brief time they touched down before going back up into a bat cloud. Just phase in, phase out, phase in, phase out really, really quickly. The only solution I could find was to throw down webs everywhere.
The caveat here is that I don't think the priests exhibited this behaviour; just the knights and spawn. I'm not certain that's the case since our group separated for efficiency, and speaking for at least myself, every time I saw a priest I freaked out and webbed or sunbursted it.
I wonder if this problem is related to the 'scorpions are less annoying' fix.
2) The final boss fight had 1 of the 4 vampires consistently bug out.
He would turn into gaseous form, and stay there. For a long, long, time.
The ghetto fix we used was to kite him (he still aggro'd, you can see his untargetable name plate) to the chamber you drop down into (with the golems and quells), and then if he didn't fix himself we'd ddoor and come back. This worked after about 2 mins each run.
3) Blades constantly having the spinning animation on the West side.
This was a problem when I last ran Vol months ago and I didn't actually check it. That said, I'm making this thread, so should mention it as I bet it's still happening.
You used to be able to use skill to time it. Now you have to guess when the blade is not "really" spinning though still appearing to spin. i.e. blind luck.
I appreciate only a handful of vets go that side anyway, and usually for the trap bonus or due to soloing, but it was weird.