The engine couldn't handle more than about 20 people on screen... I use space stations and ilum as evidence. The combat whilst relatively smooth doesn't even come close to WoW in terms of feel. I agree on gameplay, I did both initial endgame raids on nightmare and the most challenging part of them was overcoming the bugs.
I suspect your issues with finding people to group with was related to the poor quality of the PvE content, if they were interesting and challenging people would have done them. I think I did most of the single group dungeons once or twice (I forget what name SWTOR used for them) and they were interesting the first time for story and learning reasons but trivial after that, and you could gear up easier through PvP or just getting carried on a HM raid.