destro is TERRIBLE for leveling, dont go destro if your gona level.
its a waste of gold for drinking and your survivability is much lower than if ur dem or afflic because all you do is basically burst damage
ive found that afflic is best for leveling or maybe even soul link (damage is descreased by alot)
you can get felguard with dem and he just runs over everything
so def either afflic, dem, or SL/SL (siphon life/soul link)
and eventually if ur 70 and thinking about pvp sm/ruin is good and destruction is pretty good but since resilience has now taken over id still say afflic or dem is they best choice