I'm at lvl 50 guardian, and throughout leveling I actually preferred Kira. Questing and fighting went much quicker than when I used Doc. I did use Doc occasionally on some hard hitting elite mobs, but 95% of the time Kira worked like a charm and much more effectively. I also had her using the Coruscant commendation lightsaber up until low 40's. Kira is actually extremely effective throughout the higher levels.

Took me 3 tries as a lvl 33 def spec'd Guardian. I had him the first time, but my force push glitched him and he evade-reset on me and killed me. 2nd time i messed up with some interrupts but 3rd time had most of my cd's back and was easy pickin.