I think personally why the Engineer gets a lot of grief is just from the wow profession engineering. Seen it in quite a few posts here n there.
I honestly believe ppl therefore can't make the jump from seeing a wow crafting prof become a full blown "class" or GW2 profession...and therefore most of the misconceptions arise.
Theif: dunno. Love the role-back from the contemporary wow rogue to the more traditional thiefy like role. Seems to me like that type of role got lost in the rogue somehow.
I mean, almost every fantasy book has a thief like character...and while I'm not saying that every embodiment of this type of role has to reflect the main stereotypes of this role, I still think the wow rogue didn't portray this role properly or to its full potential and nor did it rly add anything. I personally think it took a lot away from the mystique of the thief.
Looking forward to seeing this enigmatic, shadowy role making a nice return.
So I'm quite lovin the GW2 thief