Wall of text ahead.
As everyone knows, Alchemist is mainly a crafting class. The only combat skill they get is Combustion, and it is really terrible (beside requiring Dig to get those materials to start with).
Worse yet, even if we were to consider its crafting skills, one thing is obvious: there is no reason to have an alchemist in party. Potions can be bought from the market, and all the other byproducts of its skills are permanent anyway. You can get them in a city, and that’s it.
While we do lack its third rank as yet, there is no reason for a player to keep an alchemist as a main character, or even just levelling it further than its third rank. As a matter of fact, with nothing to show off in a combat setting, you would be better keeping it as a secondary char and just making some other, more useful character for the latter ranks.
One way to fix this issue is by giving the alchemist some skills that are useful in combat, while still retaining the overall theme. They tried to do that with Combustion and Dig, and failed. Beside requiring a ton of points Combustion isn’t that good, but even if it was, a character interested in doing damage wouldn’t do an alchemist to start with. There are better alternatives, after all. Thus, my proposal on the matter:
Remove Combustion and Dig, and implement “throwable potions”.
Alchemists would be able to craft throwable hp,sp, and explosive potions. And use them via skills. Throw Hp Potion and Throw Explosive Potion would be given at rank 1, and Throw Sp Potion at rank 2. All these skills would have no sp cost, having a cost in stamina instead, and average cooldowns. They would have 5 levels each, with each level decreasing the cooldown on the skill. Their effects would be fairly straightforward: launch an hp potion, and you do its effect in an area (so an initial one and another over some time). An explosive one would do damage over an area, and so on.
Obviously, those potions would have to crafted. Since it wouldn’t be possible to choose the level of the potion you would launch, they may just have a single level and require Tincturing lvl 1 (for consistency’s sake, since you need it to craft normal potions). Alchemist 3 could have a toggeable attribute that permits to craft and use more powerful potions, or even just give a straight bonus (because you shake them when you launch them, and, uh, alchemy happens, and they’re better). Essentially something to make them better in comparison to the previous ranks’ ones, so that second ranks aren’t as good as third ranks, potion-throwing wise.
We could even have the skills use the best potions available and have their levels determined by Tincturing, but unless they’re made untradeable, people could just buy them and use them with an alchemist rank 1 or 2, defeating the whole point of having latter ranks. Sure, there could be attributes restricting what levels you can use (up to level 5 at rank 1, up to level 10 at rank 2, no restriction at rank 3). But it may make things unnecessarily complex, and it would make balancing the skill more difficult.
Anyway, you should have got the gist of it. Here ends the wall of text.
TL;DR: read the whole wall. It’s about throwable potions, anyway.