Silly plot contrivances? You mean like nobody in a hospital noticing a nurse that conspicuously looks like the Joker in drag? Like all the various criminal groups uniting under a "United Colors of Benetton of Organized Crime" banner? Like a school bus driving out of a hole in the side of a bank and conveniently fitting into a handy gap in a procession of other buses, like nothing about that is in the least bit suspicious? Like literally everything going on with Two-Face?
I agree Harvey being able to survive, looking the way he did, was a big stretch, but the other things didn't bother me much. Those were just your typical, run of the mill comic book contrivances.
But the ones in TDKR are silly and ridiculous even by comic book standards. At least to me.