When you can just walk in and push over Garrosh/Deathwing, it completely trivializes the lore and build up of those characters.
Keep in mind that when I talk about LFR/heroic 5 man difficulty being too easy, I'm a healer. I see the healthbars. In the 5 mans the healthbars barely budge, and in LFR they go down for about 15 seconds, in which time all you do is spam your AoE heals.
It is braindead gameplay, and SHOULD be unacceptable in a game with WoWs reputation.