I don't see any HA investing 7-8 riding though. Arabian isnt even that good you could easily save a few skill points for a better horse.
Courser is just as good, no one can catch you and you can kite all day. I see more HA use coursers.
From what I remember I went 8 riding 8 WM 5 PD and 4 HA and was using the Arabian warhorse to great extent.
Most horses can already turn on a dime, the arabian warhorse even more so, I've kept plated people knocked down for a good 30 seconds by just knocking them down then turning on a dime to do it again all while shooting at them and killing them.
I think if anything the arabian warhorse should maybe get a bit of HP or body armor, I do admit it's extremely squishy, mine would die in like 2 arrows, but it never was a problem for me.
Using the maneuvering to dodge arrows wasn't all that hard as long as I knew where the archers were, I usually waited a bit for the ranged to acquire a target and tunnel vision on them and I could have my horse last entire rounds without much trouble.