My main is a smash guardian, and I mostly pvp. Sometimes with a healer and sometimes without. For pvp purposes a smash guardian with a healer is god mode in pvp. It's one of the few classes that can put enough pressure on *most* heals - solo - to turn the tide of close battles. Without a healer you've got 3 defensive cd's that will give you 12 seconds of survivability every 3 minutes. That gets a little rough. Guardians are kick *** in huttball, and very valuable in voidstar (with freezing force and aoe blind). I haven't played a sentinel, but I play with one in pvp, and the survivability is very good, even solo ,particularly in a tank build. I have no clue about pve dps. And before you all flame me for playing easy mode - I played in beta (sage not guardian), and chose my spec long before smashing became such a thing.