Unfortunatly, casting anything will get you aggro. So why WHM then? because you can move out of aggro range and heal and then rest. With blm, you're screwed.
Subbing DRK isn't so bad, but I'd still go with warrior at low levels and white mage after 10 or so, when things like 250 damage poison duration comes into effect, and that you'll have alot of HP to heal if you get really unlucky and fail charm more then 3 times in a row. Subbing DRK, I would assume you would let your pet take alot of the abuse and then move in for the kill, but you'll still be taking alot more damage than you should for alot more downtime.
Not bad, but not the best for solo. I havn't analyzed how this would work in a party, too tired :P