I think Hisan and Gafar will work as a fast mana single hitter hero in 3* green and 4* purple respectively.
I don’t think I would hesitate to level either of them up in that role.
Now that I think about it, for my rare event team, I’ve got Berden sitting there, barely started to level up later. (In green 3*s I have Brienne & Belith, plus Carver almost finished, but no single hitters) I will probably work on Hisan first.
In purple 4*s, I’m not sure if I didn’t have Tiburtus or Merlin, I’d level up Gafar without question when I needed a hitter. I wish I had pulled him; I’m currently leveling Cyprian, 'tho I might drop him for my second Sabina. I’d do Gafar before either of those two.
These are single hitters with sand DOT, -healing, and self-cleansing.
There are direct damage only single hitters.
There are single hitters with mana steal or mana generation reduction.
There are single hitters with blinding.
There are single hitters with fire DOT or poison DOT
There are single hitters with dispel buffs.
There are single hitters with defense debuff.
And probably one or two others I’m forgetting. All of them are useful for doing damage to one target, and many do something extra, and sometimes the extra part is really valuable. Other times not so much. Depends on who you are attacking.