I also had a very hard time with my clone (engineer) my first attempt of a playthrough, I actually quit and started again to get a bit better at the game this attempt. My idea isn't working, i still suck haha. Clone throwing turrets, drons, incinerate and frigging everything else at me.. I couldn't do anything.
But yeah.. final score was :
Clone - 18 vs Ash - 1
I find it depends on class although if you have her, Ashley shines against Clone Shep.
Infiltrator and Sentinel Shep were easy, Soldier Shep too.
Vanguard and Engineer Shep are a pain in the ass (only faced them in Armax Arena though).