Atomos is widely regarded as being underwhelming… His Damage is pretty low and his revive is a) only on himself and b) dispellable.
Margaret is really just a titan specialist… not much beyond that…
Horghall also has a low damage output. Comparable to Atomos really.
That leaves only Hatter
Hatter is pretty fun to play with. Great counter to Aegir as he will steal all that defence buff & damage share and give it to your team.