I throw the balance card on whichever dps is highest on the aggro list. I know it's not the perfect tool for figuring out who's pulling the highest deeps, but other than utilising illegal software, it's the best tool out there.

I think I only ever use Spear on myself, just so I know it's definitely going to get some use out of it (I get to pull out the next card in 27 seconds rather than 30! woop!)