Near as I could tell, Chiron scaled with main hand weapon damage. Not ranged weapon damage. I think I tested white hits though and not necessarily skill hits. I probably should have done both to see if there was a difference.
I didn't look at white hits, but I'm pretty sure that main hand weapon damage doesn't affect Chiron's skills. I typically keep him at max range so he usually doesn't get any white hits in for me

. I tested his skills with and without the Oak Walker buff, and with a low-dam, nicely statted dagger vs. a high pDam 2H axe. There was practically no difference with/without the Oak Walker buff, and the dagger was much better than the 2H axe. I like to have the crit-rate buff on when I summon Chiron... no idea if it helps, but if it does it would be great

. No way I'm gonna take the time to test his crit rate though....
Speaking of crit rates, has anybody actually seen Chiron miss with Chiron's arrow? I've never seen it miss, so I've never seen the crit buff you're supposed to get when he misses....