How does one overheal exactly..?

[Lyrica_Ashtine]

Snip

Right, but also wrong :P

Overhealing doesn't necessarily make it harder for the tank unless you're seriously trying - mindless AoE healing when no one took damage, for example. If anything, it's more like a dps job constantly dealing damage;

When you deal damage instead, every point of damage you deal is equivelant to 2 points of hp restored in terms of enmity. Dealing damage may actually result in more enmity building than single target healing, but shouldn't be an issue if the tank at least knows how to press 123 over and over.