Why mark targets?

[bokchoykn]

snip

What you said has NOTHING to do with marking targets.

You seem to confuse "marking targets" with "only building aggro on one target" and "only DPSing one target".

Having numbers above your targets doesn't restrict your DPS from DoTing or AoEing the entire pack.

Marking a target communicates to your team which mob you're going to focus more of your aggro on. It simply means: "If you're going to deal a ton of single-target DPS to one mob, do it to THIS one." Otherwise, if you're tanking four mobs and your two DPS are going balls out single-target DPS on two separate targets, someone will pull aggro.