This is a simple and straight foward bug. My character was set in Heroic (25 players). Once I entered the raid and started doing bosses, I realized my drops were on ‘‘normal mode’’. I double-checked if my character was in normal raid, but no, still in heroic settings, inside a normal raid. Now, I’ve lost the chance to get the mount. I would liked a reset on this particular raid (Icecrown citadel) or the Invincible mount for the incovinience. Thank you.
Today I encountered this same bug. I entered ICC 25 man Heroic to continue collecting Shadowfrost Shards. Under my character portrait, the settings were set to Heroic 25 man but after killing the first boss, I received normal mode loot and I was notified that I was now saved to Normal 25 man. I exited the instance and checked to make sure my settings were correct and they were still set to Heroic 25 man, only when I double clicked the “Heroic” setting did it finally change the difficulty of the instance. But I am still unable to enter as I am now saved to the normal version.
This bug still exists in 2024. Just lost a weekly heroic run on my druid - set the raid to 25 man heroic legacy, entered, killed first boss, saw that the loot was normal.