Fossa is decent. And you can evolve them all, just be mindful of crew cost and being able to use actually uSE them at your Pirate level. The only real exception to this is for Sengoku currently on global, where his captAin ability only boosts characters with a crew cost of 20 or less.
When attacking normally, you always have the following: captain ability, chain multiplier, orb boost, and if the enemy color is weak to your characters color you further hit for 2x, which is color affinity.
When you're bursting, you'll also generally unleash all your specials for maximum damage. You can stack a type class booster (V1 Robin or Koza), an orb booster (Doflamingo), a conditional booster (Monet), a combo chain multiplier booster/locker (Raid Boa)... and now Tashigi introduces color affinity boosting, which will add a multiplier of effectiveness for color weakness that already exists (STR hitting DEX, QCK hitting STR, etc.)
So her special basically allows an additional boost of damage if you're using correct types. And for 2 turns, which means 2 turns of burst. She's particularly effective on Legend Crocodile teams since she's Cerebral.
