Hey guys, not really sure what to make of this one, but today I was soloing 10-man Trial of the Crusader, and after killing the first boss (monstrous menagerie) I received the achievement for completing 10 man Trial of the GRAND Crusader (10-man HEROIC). I believe I needed only the first boss of the instance to obtain the heroic achievement anyway, but for some reason, killing him on normal mode granted me the achievement for heroic. Now, I'd like it to be noted that I received normal-mode loot, not heroic, and the bosses stats were that of normal mode.
Would like someone else to test this out and see if they kill all bosses on normal, if they get heroic credit and achievement completion. Seems as though 5.2 caused a few issues with instances (after seeing the AQ40 first boss glitch) so perhaps there are other things out there like this, better start checking!