PvP at a Glance
I think it is important to go over the differences between PvE and PvP since each tank performs completely differently in PvP. They each have roles that they perform better, and since threat (and other things) become meaningless it is more about their skillset and less about how good they are at "tanking"
I do not advocate wearing DPS gear and attempting to "tank" in warzones. If you are wearing DPS gear you should be focused on killing stuff like other DPS classes and not worried about tanking. The only real use that I see from this is with the Shadow tank spec and DPS gear because the Shadow relies the least on passive mitigation (which comes from gear). People who seem to advocate DPS gear in a Tank spec believe that Guard and Taunt are all that matters to a tank - they are incorrect.
Guardian/Juggernaut Shadow/Assassin Trooper/Bounty Hunter
Role Big Baddie Beater Sneaky Survivor The Collector
Passive Mitigation Middle Worst Best
Active Mitigation Best Best Worst
DPS Ability Worst Middle Best
Mobility Middle Worst Best
Utility Best Middle Worst
Difficulty to Play Highest Mderate Moderate
(for a better formatted chart check here: http://www.tankingtor.com/2012/06/ov...html#pvpglance
Guardians are the best single target guard that exists. With their leaps they can easily engage at the front lines and retreat to cover their target very rapidly. More of a front line in your face fighter than anything - can also target a node (instead of a player) to defend and do just as well.
Shadows are equally able to attack an defend. Very useful in a group with multiple stealth characters to help cover an attack by strong DPS - also very possible to solo attack a node against a single defender. Give a false sense of security when defending by watching from stealth and striking at the opportune moment.
Troopers work better behind the front lines, protecting other ranged classes and still outputting some DPS on people who don't know what hit them. Definitely healer spotters and killers. Find and pull a healer into the DPS face and get them to notice.
This is the controversial topic where many people feel that tanking stats have almost no effect on PvP. I'm of the opposite opinion but I don't think the debate will ever be settled. Shield and defense have less effect here than in PvE, but they do still matter - and you will see a difference if you stack them.
Active mitigation, no question has a place in PvP, so looking purely at active Mitigation you'll see that the Shadow has the edge. But armor plays a large roll here as well since it does block most attacks - so the lower your armor is the more damage you're going to take. This leaves Shadows far behind int he survivability department.
Guardians also have access to "Focused Defense" in PvP that they don't have in PvE (while tanking). Since it acts as a threat drop it's difficult to use while trying to maintain aggro - but in PvP you can use it while stunned to get a small boost in self healing. Blade Barried also performs excellently since it absorbs damage types that would otherwise completely bypass all defenses.
Troopers rely mostly on their heavy armor here since they have the lowest defense but highest shield rating. Smoothing out damage isn't as big of a deal here as just being able to take as much damage as possible. Troopers do have the largest health pool to work from - which gives them a bit more of an edge. Unfortunately their active cooldowns are lackluster and situational leaving them slightly more exposed to focused fire.
DPS Ability -
This does matter in PvP more than it matters in PvE. My Guardian will never be at the top of the DPS charts (though sometimes he comes close which scares me).
Vanguards have the clear edge here because much of their damage ignores armor, which is the only thing many characters have to mitigate damage. They also have access to the most AOE attacks, which when used effectively can really pad their damage numbers.
Shadows are a close second, again with access to AOE damage and mostly Force attacks that bypass defensive stats and go straight to armor.
Guardians while having the lowest overall damage also do the most weapon damage (blocked by defensive stats) - which means against other tanks they're even worse off.
You see a little change here because of the way warzones work. All of them encorporate some type of jagged playing field with multiple levels to work from. This gives an edge to Guardians who have two leaps to more easily navigate these different levels.
Shadows fall behind a bit because they lack gap closers, they have to rely on stealth for an initial closer, then fall back on their sprint for subsequent followup.
Vanguards once more top this chart due to their ranged attacks, pull and leap.
And with superior mobility comes lack of utility. There isn't much that a trooper brings other than the obvious. They have no knockback, a single stun and have a hard time in a "support" type of roll.
Shadows sit in the middle here mostly because stealth is a huge game changer in PvP where you are playing for objectives and not for the scoreboard.
Guardians have the most utility skills, which makes them the most effective at keeping people busy and away from critical targets (read: healers). They have a way of making an impact in a battlefield and keeping people focused on them rather than objectives and/or other players.