Having only played 1 game with a vanguard at level 8, I am limited but still have some thoughts in this:
When I think of the Vanguard, I think of riot police, or those elite personal guards that high ranking officials/nobles/royalty would have escorting them and protecting them. Thus, I can see Diplomacy being a class skill to talk people down (with intimidate being useful for hindering enemies in combat). Life Science, not so much. Given their description and how they operate, I can see Physical Science.
But my biggest peeve with class skills is the total lack of engineering, especially since they are able to weild advanced melee weapons and wear heavy armor with shields. You’d think they’d be able to maintain equipment that regularly takes a beating. It would also help to expand their Starship Combat capabilities beyond just shooting things if they need to. No complaints about skill ranks though. Base of 6 per level is just enough without being silly.
Aspects, I think are beneficial. A free CM feat and a bonus to a skill can be quite helpful, as I’ve experienced. Didn’t even need to build into Strength for it, yes at “high” level. But the Catalyst comes in far too late to be a real help. And hinders not only playtesting, but defensive and protective capabilities from the aspects. Granted, I went with Boundary and Exergy as a damage sponge build and ended up making light of nearly all damage from the enemies in my attempt to basically play my own krogan. But it was really fun. These are my only complaints so far and may be back with more feedback as I get more chances to play (especially when I’m not in SFS and can do multiclassing to help with that end)