I always thought it kinda odd that you can kill Malygos twice, or kill Jaraxxus up to 4 times in a single week, or kill the LICH KING twice a week. I love how they are mixing the best of WotLK with the raiding of BC
WotLK: raid flexibility for 10/25 mans with appropriate gear
BC: only one boss kill per week (otherwise lore gets so messed up, it'd be like seeing 2 Arthas')
The similar loot is the only thing that troubles me. If you can get, say, ilevel 325 gear from 10 man Grim Batol, and 325 gear from 25 man Grim Batol, what the hell is the point of coordinating 15 extra people and fighting bosses with a less forgivable enrage and abilities?
In its current state, this will nail down the coffin on 25 player raiding since there will be no bonus incentive, although 10 player raiding will really start to take off more than it is now. Also, lore-wise, this change makes SO much sense, compared to the ridiculousness of WotLK lore in raids.