Juggernaut/Guardian - By far my favorite class. Best class for wzs imo because you get a 4 second immunity to CC on charge, taunts and a friendly charge that counts as a taunt, aoe slows and with amazing amount of consistent DPS
I feel guardians have a lot of variability due to difference's in spec. And after trying out FOTM focus for a bit I really missed having that 4 seconds of CC immunity. But the differences in the specs means you can have vigilance for great consistent dps and tanking abilites (focused defense cd ftw), or have focus for a greater burst capability at the risk of being a glass cannon.
Though an undergeared vig guardian will have a lot tougher time dealing with healers or other high burst classes then an undergeared focus guardian.
Gs/Sniper- Awesome burst ability. If played well can be very mobile. Only thing is 99% of them dont play mobile.
I've only got a lvl 34 sniper but from what I can tell only 1 spec can be truly mobile and that is lethality and it is incredibly mobile compared to a MM sniper (basically a turret) and slightly more mobile then engineering which needs to be in cover to set up its burst. Lethality also has a lot of defensive and cc abilites at a reduced cd which helps nicely.