Raid Leader has not killed LK on 25-man
Before a given boss (or even better - if noone in guild killed LK25 - just at a start of instance run) - try setting the difficulty onto heroic - of course it will fail with an error message...
it is however fun to notice that even though bosses remain on normal HP/dmg/skill wise, the game somehow "thinks" you actually set the instance onto heroic - there is the "heroic" skull on entrance, people dying and releasing cannot enter instance and the most important part:
shadowfrost shard drop chance seems to be increased to the level of heroic difficulty (which is around 90%?)
when we were still without LK25 kill and just cleaning ICC, we got 10 shards on 11 bosses - while all on normal...
ye - it MIGHT be just awesome luck but seems to be more then that...
(a possible factor might be that RL did not have LK-25 kill, but had LK-10 kill; the "setting on heroic" was actually attempted again should a wipe occur just to be safe)
could not check it again since we got the LK25 kill and are now progressing on hard modes but seems to be "not working as intended" ;-P