tbh for both pvp and pve you'd be better off going afliction as dest (especially the primary dest build, 0/21/40) has very high stat 'requirements' for it to work well in pve (and tbh, it just doesn't work well in pvp... depends to much on critting which is now impossible in pvp)
the minimum requirements are, imo:
hp and mana of over 8k before buffs
minimum 170 +hit
minimum 20% crit including devestation (so 15% crit in your character screen)
1000 +dmg including felarmour
now remember, spec what you enjoy. but if you want to spec what's best for your gear level. go something along the lines of 41/0/20 type specs until you can get to the above stats, after which you could find dest being a better dps spec for pve. for pvp... well there aren't really any 'specific' specs.. a
7/19/35 or
5/15/41 and other similar variations could be viable in pvp. but you generally won't crit. you generally won't get to cast many spells and will be relying on backlash procs and you will almost definately need a very good healer with you.