Apparently C-3P0 either had hidden combat programming or his head was smart enough to be somewhat compatible with the battle droid body in terms of software. That being said, if C-3P0 can get a few precise shots while Etima Lumas is leaping around, he dies. If Etima Lumas is actually smart and can deflect something, he could maneuver around C-3P0 or maybe force push him the same way Kit Fisto did.
So, they are sort of equals.
I doubt that 3PO has hidden combat programming, Anakin made 3PO from scratch, and after anakin left, cliegg lars own them and i doubt they were smart enough to program 3PO and they were sort of pacifists. and Ani as a boy was the nicest person you would ever meet he as qui-gon said "had no ill will toward other or need for a reward" or something like that. so its just not possible for 3PO to possess any combat training,
I think Anakin had all kinds of secret terrorist commands stored in C3PO's head. Remember.. He is the one who grows up to be a sith and was clearly a sympathiser of the bad guys.
Little Anakin probably planned on making C3PO teh über overlord on assassination allowing him to finally kill those annoying kids who grew up to be dumb bounty hunters!
What a revelation!