You can fully sustain blood barrage bandos on osrs. Asianricecup osrs iron man did it last episode for a 30 kill bandos solo trip. Which he says is the best way to solo bandos. As for magic damage, I was hitting 41s with blitz which is broken. The nerf he did fixed it which is why I'm saying don't touch damage. As for accuracy in PvP, go ask any 07 pker how rare it is to splash in max mage vs someone with a black dhide top as their only magic defense as well as wearing rune with range prayer for 15 wilderness levels. They will say it wouldn't and shouldn't happen.
Please do some research on PvP interactions and how magic works, watch ditterbitter videos because he literally rages after splashing 3-4x in a row because it's pretty uncommon to splash that many times on wrong prayer.
I don't know how all bosses are meant to work but bandos 100% the solo meta is barrage and bloodbarrage, giving you the most kills per trip. I'll link the video here if you like: