Thrust.

It replaces Arrow Bomb in 95% of the situations you used to use Arrow Bomb in 2nd job. I don't know why that seems useless. Maybe Hurricane might look flashier when taking down large mobs, but Inferno is still the superior skill to use.

4th job itself makes Arrow Bomb obsolete. I took it off my keys shortly after I advanced to Bowmaster (took off Arrow Blow and PKB, too). I was able to start at Newties right away when they came out, as a BM. Using anything but Hurricane + Hawk at Newties is awfully pointless. I threw in Arrow Rain a few times, but Arrow Bomb or Inferno would have just been slow. Newties easily and quickly carried me into the 14x levels, which is when I was able to pimp up my training to SKPTs.

Using Arrow Bomb or Inferno for anything other than a (waste of time) lure would be silly. There are never mobs of more than 3-4 in a regular party, unless you stop killing for a while or something. Heck, even training with 1-hit Bishops doesn't produce spawn fast enough to get ahead of me. Using Hurricane is much easier and more effective in SKPTs. I just bounce from one target to the next to the next, etc.

I'm an extremely melee-style Bowmaster. I hate "safe spot" or "standing still" sniping. I like being reckless and crazy! My training heavily incorporates Mortal Blow, with an extra spice of Arrow Rain. I can kill Skeles so fast that it'd be wasteful to ever stop moving. I'm always walking and Hurricane-tapping back and forth while training. Since I'm always moving, I'm often in MB range of monsters (whether it be getting close to them or having them spawn near me) and use the MB + Hurricane combo to increase my killing speed and style. If mobs ever do build up on/around me, I'm usually already in them anyways! It'd be wasteful to try gathering the mob with DB and then Infernoing them or whatever. I can mow down an entire mob with Arrow Rain in a couple seconds while only getting hit 0-2 times. I rarely (very rarely) use Dragon's Breath. I never use horizontal luring attacks like Inferno/Arrow Bomb.

If fast and furious training means more pots, so be it! It's a heckuva lot more fun than being all tidy and building mobs and trying to avoid getting hit by staying away from monsters. I avoid being hit by killing them before they can even react (or taking advantage of my high avoid, hehe). ;D