if you show a little patience, the void can keep aggro the whole time. throw CoA to pull it, and at the same time sic your void on it. he'll taunt the second he gets in range, so he's got aggro now. wait a few seconds and let him taunt again. then after that, the next time he casts the taunt, throw Corruption, then Immolate. Even if Immolate crits, you will still be fine. then, you pick your poison to burn the mob down. I prefer SB->Conflagrate->Shadowburn, as 9/10 times one of those will crit if the immolate didn't, and it's easily 1500 damage unbuffed (those three for me at 61 hit for 750->700ish->700) it's mana intensive, but when you get low on mana, CoS, Corr, Life Tap, Drain Life will down things quickly too. If you spec heavy destruction and pick up things like Nightfall, Siphon Life, Shadow Embrace (only if you have Improved Drain life), and Improved Life Tap from the affliction Tree, you'll be able to keep grinding with the LT/DL combo and still dish out the pain.
after typing all of that, i remembered: the most important thing to look out for is if a "Resist" pops up over the head of the mob when you didn't cast anything. It usually will mean that your voidy's taunt was resisted, and blah blah blah just get KLH Threat Meter. You won't have to worry about unexpected aggro then.