Thrust.

AR is the only skill Bowmasters get that has no minimum range. You'd have to be absolutely insane to skip it. Even in 4th job there are instances where you'll be in a crowd for a while, you know you'll be in a crowd for a while, and you still need to do something about it.

Example: I don't think it would have been possible to solo Zakum without AR. I have an NL friend that actually had to equip a Dagger for a while while he solo'd just to get rid of the summons. It's also important in places such as HT, when a black Wryvern is coming from below you and it needs to be dead. Sure the Bishops are supposed to Genesis when they see Wryverns, but no one's perfect.

I was mostly speaking from time spent on a Sniper, Arrow Eruption is annoying because it has a different range than every other skill you use, I found it easier to just keep off mobs than to rely on Eruption when I wanted to kill them.

I wouldn't be just straight up getting 0 AR, I think even maxing everything except Thrust there's room for at least 21 points in AR. At that point it's still 90% as strong as lv.28 (even closer including crit/SE since afaik they're independent of base damage), so enough to deal with Zakum summons hopefully.