I've used Doc since he joined my "leet" crew, and I've never looked back. Kaliyo is nice but I finished my class quest 3 levels early with Doc at my side. Elite mobs, 2 levels above me, were super easy to handle. There is hardly any down time with him as well. I typically finished fights (including gold elites) with 80% or more health. Also Doc is great at crowd control. I don't recall what level you're at, but around 46/47 the mobs start to increase, especially around elites. I did make sure he had some nice gear, so I'm sure that helps. But Doc was so good with levelling I didn't even bother with Scorpio. Now that I'm 50 i'll start to suit her up for combat.