Commendations are luck of the draw.
I've had dungeons where I ran everything flawlessly, held aggro on every mob, faced the enemies the correct way every time, pulled managable mobs, zero knockouts, speedy run, every chest obtained, skipped non-essential trash mobs.... zero commendations.
I've also had dungeons where I basically ran through on auto-pilot, made a ton of sloppy mistakes (but no one got KO'ed) and got 3 commendations.
I think that in the long run, it all evens out.
I generally give my commendation to the person whoose name I like the best
As far as the OP's suggestion, maybe it's something SE could look into. Given that commendations are kind of an "icing on the cake" aspect to the game (they aren't really essential to anything), I don't think they will put too high of a priority on any adjustments. It doesn't hurt to put out suggestions though.