Shadow Priest PvP while leveling?

[itwasfree]

Howdy,

I plan to heal at 60, but will be leveling shadow because I'm not a masochist.
One of the things that has always bugged me is when I'm playing some classes pre-cap, being unable to gank 6/8 classes because of pre-cap weakness (due to skills/gear/poor open world pvp toolkits).

Obviously, shadow priests have pretty good anti-gank utility, but do they have the ability to finish off targets that they happen to stumble upon out in the open?

Examples:
Hunter opening on just about anything sub 50% health. That target has zero chance to run.
Rogue opening on Paladin (at any amount of health). Why bother?

[Ana]

If you get close enough to fear, just about anything dies easily (except undead which are basically immune to priests). Assuming you already have shadow form. But then if you're putting points in shadow tree before 40 you aren't leveling shadow, you're just wasting talents.

[Sonasol]

If u not oom and the target isnt to hight to resist your spells you will not have problems with any class exept maybe palas and other priests. Palas because they can dispell yours dots.