Hmm i think all the dps should watch over for the aggro they make first of all and they need to give u some seconds for make the initial aggro on the mob or boss.
But there are situations when they need to full nuke as at Illidari Council so there is your job to keep the aggro (specilay if gonna tank the Paladin).
That is my opinion maybe is not 100% right
And mage's who use Pyro Blast with regularity are some noobs. (exept Curator's evocation)