With all due respect, I think you're DPSing wrong if you're having a problem with 1 strong. I often solo strongs that are 2-3 levels above me as Lightning spec, while Khem is off selling my trash items.
Unless you're talking about Elites, you're clearly doing something wrong. Bubble before the fight, use electrocute when it wears off, you should be able to shield again shortly after electrocute wears off, but not many strongs live that long against me.
I'm level 28 now and haven't had any problems, the only reason I ditched that damn pirate was because a) I hate his stupid face, and b) he does **** for DPS, I think he only does like 5% more than Khem.