Depends if you like straight up cooldown usage vs managing stacks vs eventually managing 2 resources(MP and TP).
Straight up pop a cd and keep going is gladiator/paladin. You will get a spell for healing a party member/yourself post 50 but that's about it for healing besides bloodbath from marauder.
Marauders/warriors have a few cooldowns but also need to manage their wrath stacks later to use either as damage cd, aoe enmity+damage, defense cd. It's a fun job and has a very easy time of holding aggro(overpower once, maybe twice and you tend to be good). A lot of self-heals.
Dark knight - you have to manage MP use with mp regain and mp use skills, at the same time you are also using TP. From what I understand has some intersting comboed moves later on.
For low levels if marauder overpower is better at aggro than flash generally - but flash works as well - just need to use it a bit more.
Also overpower - frontal cone vs flash 360 aoe centered on you. Use the best tool when you need to.