Thrust.

anyway I meant to ask if it's possible to skip AR in favour of Inferno, or if there are range/map reasons not to (I think squids and gobies might be fire-resistant? Know they're not weak to it)

Inferno is much more useful than Rain in 4th job, because you are no longer helpless when stuff gets in your face, and things rarely get that close to you anyway, thanks mostly to Dragon Breath, but also to Phoenix and Hamstring (I don't have those skills yet, but I assume it would be reasonable to assume that). I didn't put my first point in Rain until level 90, due to my heavy point investment in Strafe, Inferno and Puppet. It's not a necessary skill by any means, just like Inferno is not necessary. There are enough training spots in 3rd job that you can get by without it.

However, there are still cases were Rain is undeniably useful. You are not always capable of keeping mobs from surrounding you, especially at Typhons, and at Zakum. This is where Rain shines. Arrow Rain is also superior to Inferno in most early-mid 3rd job training spots, such as Pirates and Wolf Spiders. This is why early Rain builds are not nearly as rare as early Inferno builds. And Inferno alone does not fare nearly as well as Arrow + Inferno at Himes.

Throwing a few points in Rain (up to 9) is understandable from my perspective. Throwing the entire skill is suicidal. I only consider two active Hunter/Ranger/Bowmaster skills completely replaced by level 200, and they are Arrow Blow (replaced by Double Shot as soon as you get it o_o) and Double Shot (replaced by Strafe at level 70). Jump-strafing is still helpful once in a while, and Arrow Bomb still gets an occasional tap when I'm fighting fire-resistant mobs. Even PKB is still useful, mostly against flying enemies that I can't hit from a grounded position.

I think Hunter/Ranger/Bowmasters who don't make use of their full arsenal of active skills are not using their whole potential. Most of our passives have very limited potential: Blessing is completely useless, FA is considered by many unhelpful and completely replaced come 3rd job, Thrust only adds the easily replaceable stat speed, and MB only helps when monsters spawn on you (and with Hurricane, but again, it either doesn't work for me or I don't get how to use it).

AR is the only skill Bowmasters get that has no minimum range.

PKB has no minimum range and can be used in mid-air (and pushes monsters much further away, where you won't suffer touch damage and where you can link into your more powerful skills). MB helps in the rare instance a monster spawns on you and pushes monsters out of minimum range, and your 4th job skills are typically enough to keep monsters off you and out of minimum range.