1-2-3 combos are really just busywork to keep you engaged while your more important abilities are on cooldown. I don't know about others, but my entertainment comes from boss mechanics rather than what buttons I'm pressing. I agree that consolidating the busywork buttons down would allow for more complicated boss encounters and more impactful abilities to be added. 1-2-3 should be basically like our autoattack (and in fact GuildWars2 already does this, your number 1 combo is essentially just your autoattack)