This ones pretty major (at least to me), none of the mobs added by Thaumcraft have any aspects set on them for some reason and it affects content like the crystal drops obtained from liquid death. Maybe base off their set aspects from 5 to fix that?

Vanilla mobs have aspects as normal.

Well going over the source code it looks like Thaumcraft is trying to register aspects for Thaumcraft entities (common/config/ConfigAspects), even for things like Flux Rifts, but I guess it's not working for some reason. Still, does make choosing aspects easier.

The registration done by Thaumcraft wasn't working because the aspect registrations were done in the form of Thaumcraft.<name>, but the entities were actually just registered as <name>. This isn't referring to the registry name, it's a separate name (although registry name would probably have been a better choice - I'm guessing this was ported from a version where registry names didn't exist).

@TheCodex6824
Works well from testing, there are some entities like lesser crimson portals that could use aspects, I might make a list on that.