I probably haven't figured many of the combinations out since i tend to use a very limited amount of spells. I should start using more of the glyps, hexes and stuff.

to continue on the affliction stuff, death hex is an awesome spell. It makes all melee attacks critical, so with both my warrior and Zevran hitting stuff from close up, even bosses would go down quite rapidly.

As for spell combinations, I picked up a few more.

Grease + firestorm = more fire. Good stuff.
Shatter - if you freeze people and hit them with the stone fist, they shatter. Instakill ftw.
death hex + death cloud = ridiculous damage. Seriously. Like 600+ damage per tick. Instant death for most baddies. That was actually an accident... I death hexed someone, and then a darkspawn cast death cloud and the creature practically blew up.

600 damage?! That's even gonna hurt a dragon! I gotta try that. My (blood) mage is a hex/necromancer type of guy so he's into those spells.

yea, I plan on making my party caster heavy... me + morrigan + wynne and a rogue. Since I'll be arcane whatever I can tank. I will definitely have death hex and death cloud at least once, maybe twice. I've also unlocked spell might and plan on unlocking tempest (lightning storm) and blizzard (ice storm) so I can make one of the final spell combinations I haven't done yet.

Spell might + tempest + blizzard = storm of the century. Supposedly it has it's own insane animation.

Also summon skeleton + spell might = super skeleton. I'll be getting this one shortly, as soon as I can unlock the 4th spell in the skeleton line.