Well, we don't know what monsters you have in a general way :/
I think you have to change Dagora. He is very safe but he is not helping your teammates directly nor dealing enough dmg. He is just almost unkillable. Especially knowing you have Acasis (Wind Sylph) which makes your team tanky enough to don't need something like Dagora. Even a 2nd healer like Belladeon or Ahman would bring more to the team, more survivability and Belladeon would at least be a Defense breaker, which is important to have (and he also boosts ATB of 30% with his 3rd skill).
I would bring another damage dealer because of this Acasis, but if you still want a tank to decrease enemy's ATB like base attack of Dagora, I suggest you to get Shailoq, the Water Serpent. He is tanky and still Water type, but he decreases ATB of 30% to all enemies with his 3rd skill, he decreases one enemy's ATB again with his 2nd skill and he removes beneficial effect on his basic attack.