Right, as Guardian also you naturally take less damage (less healing needed) while Balance basically all of the mitigation comes from healing only. Also the higher dodge rate means the debuff stacks slower (though from what I know, it still will hit 96% in good time).
I mean, optimally if I wanted to solo BoT I'd go Guardian, but can't be bothered setting up bars + gear esp with level 100 (which will make all of the Cataclysm content easymode) in such a short time!