Asterios: He isn't the most ideal support for an Arts team considering he has only 1 Arts card, meaming you can't Arts Brave Chain even with his NP. However his kit provides decent buffs for the team and his NP gives good debuff for the enemy team.
a Servant with an absolute joke of a skillset (seriously, why have Mental Corruption if the accompanying skill/effect he gets doesn’t come out until later? And why is his Aesthetic Appreciation so pitiful?) ... DW, Give him at least two strengthening quests and i'm fine with it!!!
It's because she needs a lot of support to reach her full potential. She's not a servant you can blindly jam into any team and expect her to perform optimally.
Compare her to Jalter, for examp. Jalter melts anything as long as you have crit stars and can push the big red murder button, but Squirturia needs someone like Tamamo or Nero Bride (preferably both) to achieve truly nonstop NP spam.
Also since he used a "Self-Destruct" Noble phantasm at full power and suffered no real wound, his NP should be an NP that uses every other Servants NP in the whole game at 500% charge and level 5 automatically aswell as an extra 1000000% death resist so he doesn't die
"NP DAMAGE UP
Bringing Tristan’s NP damage up, this type of CE is best used when Tristan’s damage output is needed - either as a primary damage dealer, or in multiple-boss stages containing a Saber-class boss."
What has Martha to do with Tristan? LOL
Actually, her third skill works against all Saber enemies. At max rank, she does as much damage to Saber enemies as Archer class Servants do, and it boosts her star generation as well.
It's still a niche skill, but not as much as you're making it out to be. It's her NP that only gets bonus damage against Saberface enemies.