Greetings,
In the past 2 resets, We've been doing heroic Gunship on our alts despite the fact that only mains have killed the Lich King.
The method is simple, have someone who can unlock hardmodes be the raid leader, unsaved and standing outside. Once the raid is at Gunship battle, just ask that person to switch difficulty to heroic and you'll be able to do it on hardmode.
The idea is why this is useful is that you get access to item level 264 (10) or 277 (25) without having to kill LK. Just pay someone who's not saved to be your raid leader and it will be done.
The good part is, the raid leader who is not saved won't also be saved to ICC and he can do it himself with his guild later on that reset, or give access to heroic to another group.
Gunship on heroic is as pathetic as on normal mode, so it's still free loot.
Tested and still working as of Wednesday 17/Feb.