Are Darth Traya or Sion viable?

Traya's isolate is very useful in many situations, and many counter teams include her solely for this ability. Stops counterattackers from countering, healers from healing/reviving, taunters from taunting, supports from spreading buffs. She's also useful for removing debuffs on sith.

Sion is more niche, but a solid tank and debuffer. You'll need good sith to take full advantage of him, wheras traya is more of a plug and play hero.