I'd have to go with Druid / Sapper / Warlock (No specific order), due to their gameplay being so fitting to my own preference.
With the Druid, I could keep up a high DPS as well as still maintaining the health of both me and my allies without any problems at all.
With the Sapper, I can just sit back and relax and deal plenty of damage while still maintain a safe distance.
With the Warlock... Well... It's Warlock. I can't complain at Warlock in any way. I love it. And I'm rather curious to see what the updates for Warlock will do for him.