Top Tier: Summoner,Invoker, Sorcercer, and Sentinel are the top of the Group pvp ladder. Each of these provides a ton of utility and synergize with other classes extremely well.
Mid Tier: Savage, Overlord. These guys provide some utility but their skills either don't provide the mobility needed or conflict with other classes combos.
Low Tier: Twin Fighter Destroyer Ninja These two don't really bring anything to a teamfight other than pure damage.
Weird Tier: Dragoon, while they provide a lot of CC with their attacks they really can't do much vs multiple opponents without just ruining combos for everyone or getting their own combos ruined. Where these guys go depends on the Dragoon's playstyle and their ability work with their teammates.
this is just my personal opinion.
Low tier has a few points you can vouch for to bump Twin up:
-Twin brings a lot of stun locking and super armor canceling. Which doesn't interfere with DPS.
-Ghost Fighter and highest movement speed enables them to be exceptional at high movement speed targets. Whether it be other Twins or Sentinels.
-Weave, despite it's nerf can allow for decent reduction of risk.
-Training Time is essentially it's own freeze and The Ring from Hell is a good AoE slow.
Just a few points that'd make twins at least the highest of low tier or even middle tier.