Yeah, on my Trooper I didn't always rely on solely my healer. Being tank-spec and hard to kill as is, if I was overleveled for a quest I'd just take my main dps guy instead to better quickly take down foes(since as a tank my dps was pretty crappy).
I assume you could make Doc better at combat just by getting him better gear that favors his stats. In Doc's case I think it's Cunning Medium Armor(Smuggler gear), so that gear would help both his healing and dps.
Though overall I'd guess he won't be a top tier dps, which makes you be more tactical about whether you get more benefit out of having a healer out to keep you alive or a dps to help finish foes. It's all up to you.
"Sir,we are beginning our search for these rumored 'underwater villages'.They will not stay hidden for long". -Battle Droid Commander OOM-9!