Destruction does have a lot of nukes...plus the AOE stun (forget the spell name now) could come in pretty handy for dual boxing. I'm thinking do the stun...then several chain lightnings at once along with a rain of fire....could be pretty nice.

However, demonoloy is pretty good for the felguard...he does do a lot of damage and when he crits, he'll increase the spell damage of the group for a time. Mine crits very frequently. Demon form is a good one too for the increase armour and immolation aura if people start getting a bit close + the 20% spell damage buff is also nice.

I probably haven't helped here.