I had no problem getting a raid spot in sunwell :3
It was spell damage? or crit.. one of those.. Then they gave it to warlocks' shadowbolt...Anyway, back in those days, Scorch increased all Fire damage taken on the target. I can't remember if the stack was to 3 or 5 (it's admittedly been too long for me to remember every damn thing), but we were there to really just buff our damage, Destro Lock damage, and Ele Shaman damage. Once that was up, you'd simply spam Fireball.
Warlock damage was through the roof when they had a shadow priest.. good synergy with the shadow spells...
Going WAY BACK... Mage ignite stacking? ;D