This is going to sound weird, but as a Sorc healer I find the easiest class for me to go up against 1vs1 is a Gunslinger/Sniper. Why is that?
You're one strange sorc then!
I find it is easier to kill sages/sorcs than any other class with my sniper, especially the healers since their dps is so low. Of course they will try to heal themselves, but I can easily out-dps their heals, I feel it's part of my job as a sniper to do that. Next easiest for me are the marauders/sentinels. Probably 3/4 of all the solo kill medals I've ever gotten are from killing a marauder or sentinel. It's because we're built to be their kryptonite. Many times I've kept them at distance through roots/stuns/kbs that I've killed them with over half my hp still intact. Looking back now, it's hard to believe I actually used to fear them back when I was a very young and inexperienced sniper, and I panicked when I saw lightsabers waving around, but that was so long ago.
The only time I have trouble with them if they use their cheap Houdini trick which is the only thing I think is OP about them. The only classes I really have trouble with as a sniper are assassins/shadows and dps scoundrels/ops. If there are two or more of them on an enemy team and they notice me, it can really make my warzone hell.