Actually Red Monika is an Evasion Tank. As in you should be rasing her Evasion score as high as possible. She has a Taunt too, but it is an ability and not an action like Gully's. So you are a bit off about the tank part. Red Even has a Cleanse as well, but again tied to a slower ability and not an action.
Red is a Status Effect monster who uses Stealth and Taunts to lose and gain aggro as needed.
And Knolan can heal just as good as Calibretto if you spec his Perks right. He functions best as a jack of all trades. He can cast shields that do status effects to the enemy, Heal, mass heal, and stack tons of magic damage. And to be honest, he is just as squishy as Garrison. And Garrison can be pretty squishy.
You will get one more character too. I have not gotten him yet so not sure how he functions.
As for party comps, I would suggest staying with the Holy Trinity of Healer, Tank and DPS.
So Gully or Monika as your Tank
Knowlan or Calibretto as your Healer
And I assume Garrison or the new guy as your dps.
And this is before even getting into how you can switch up these roles a little with the right gear and perks. And Red is more than capable of pushing out mad damage as well as being impossible to hit with her Evasion Abilities.
I would suggest just experimenting with different groups. No penalty for leaving the dungeon and going back in with a new group. Even though I wlll admit that I consider Gully the MC so I usually never take her out of the party.