Tsnade is unique in that she can be placed in the frontline if you need her to be. Her chaos crit really can be a crucial game changer. She deals a surprising amount of dmg as well.

Sakura is a good healer, just don't use her on auto. Her standard heal doesn't clear debuffs, which means you need to time the mystery well.

Karin is an offensive healer, but I think she falls in favour late game.

Kabul like others say is probably one of the best healers for f2p players. Provides extra walls with clones and heals himself double rate.