Wasting an aetherflow stack shouldn't be anyone's concern, yes, it punishes you to insane levels, but come on...festering a boss without dots or casting bane on mobs that are far from each other? Talk about failing...
Now, I don't mind even this being changed, make it so that fester does base damage and does increased damage for each dot you have. Bane...just give it something like 20 potency in AOE so that the spell never fails.
You do that and SMN is still hard as f*** to do good DPS with.
On my other reply I was addressing the real stuff that would make SMN less punishing. Not these little irrelevant things like "no longer sustain!" some people like to go over and over...