Honestly, how did Blizzard think that Champion packs would be balanced? In Inferno, the Champions get 4 moves. For the sake of the argument, we'll make a WoW-based analogy.
You [Mage, Lock, Hunter, Shaman, etc.] are facing a random team of 4 enemy classes. These classes are 100% random, but you will have 4 unique classes/specs.
You'll have plenty of easy comps to face (since it's randomly generated), such as Prot War, Prot War, BM Hunter, Blood DK. That being said, due to the same random nature that can spit out Prot War x2, BM Hunter, Blood DK, you'll occasionally run into Rogue/Mage/Priest + Lock or Hunter/Rogue/Feral/Enhance. Thus, your experience and the difficulty of said experience can vary substantially in the same difficulty setting due to the random nature of the game.
So, how did Blizz expect this to seem balanced? There's little-to-no reason I should be running through any Act at a constant pace - only to be confronted with a mob several times more difficult than anything encountered thus far for no reason other than RNG.
/rant