I think either the assassin or the guardian. With the assassin you can hit high and dodge attacks with your work on your speed. And the guardian is very well balanced in both magic and melee attacks... Like your medic partner.
Personally, I think gunslinger is the best, but with all of the cheats it doesn't matter because you can just hit 50k after using them for about 10 minutes.
I use Guardian and I think it's the best. Very well balanced and you can choose the mage way or the melee and either path you choose you'll be good at it.