Neither one is better, they're different play styles. Pick the one you like. At 55 yes sorcs will almost always be top damage if they're good, but overall damage doesn't mean everything. I've been top damage on my sorc many games by running around and making sure everyone on the other team has affliction on them before actually picking out a value target to focus. Dot's are what makes sorcs and dot spec'd ops and snipers so easy to be top damage. Doesn't mean they actually helped the team out with what they did. I will say my marauder does die more than my sorc and jug, but he's also probably the most critical help to any team, as good marauders spell death to healers in wz's, as I know from my sorc heals, nothing worse than having a skilled marauder pounding on you when most of your team isn't helping you kite/peel... guess what they don't get heals lol.
As far as positioning goes, that just comes with the territory of playing with pugs. Yes, in most pugs people ignore all sense of pvp and target whoever is closest to them, even if it's a tank spec'd player... So yes, if you're a marauder and you jump in first, prepare to die quickly lol. Let your team take a little agro first, in pug wz's it's almost like pve lol. If you actually face good pvp'ers in those warzones however, being a sorc is far from easy, as you WILL have at least one stealthy on your butt the entire game (if you're worth the effort anyways). So if you're lightning spec'd? Good luck getting one of those casts off with an op and an sin on your butt.
What it all comes back to? Playstyle, pick the one you like and run with it. Or be like me and lvl up everything