Ran a heroic life of alchemists with the vile chemist/vistani thrower approach which was decent. Not the even kinda overpowered state that most classes start in, but decent.
However I noticed that the orchidium reaction spike is pretty hardcore, being like +70 PRR and extra elemental resist. Added to the +40 PRR you already get from orchidium and some more from the various trees and you're getting into really tanky territory. Saving throws being a one-stat wonder are going to be good.
Typically if orchidium is your desired state, you find yourself leaving it whenever you want to heal, which is yellow. I know a lot of alchemists prefer to use heal scrolls and wands for that reason. But the 12 seconds of hyper PRR is pretty nice. Consider:
Orchid spike ends with casting of an AE heal of some description. You're left with yellow primer.
You cast a wave of poison (cheap, and blue). This gives you a green reaction spike. maybe you use the green spike to heal a little more. or maybe you
Use a red spell or ability (the poison shot or strike thing is free, and red, or you could just nuke something, using a red poison nuke will even make use of your green spike and you have several of single or AE type. Red gets you ready to get back into orchidium with a blue use
Cast another wave of poison---now back in orchidium.
so to get back to orchid and spike you need blue/red/blue. You can probably do this most of the time in 3 seconds or less.
Perhaps a rotation where you
<do blue/red stuff while in orchid spike state>
<when spike runs out, toss a heal somewhere, if don't need a heal, smoke a yellow nuke or CC or utility, but honestly, somebody probably needs a heal or while by the time the bottle arrives>
Punch a wave of poison on the stuff you're tanking. If for some reason you don't need or want to do that, you can use another blue spell. Thing is most blue spells have fairly high mana costs. A defense bottled boost might be good here.
Do a poison nuke here like poison breath. Did you notice that you removed poison immunity for most everyone in the area of effect at the previous step? If economizing mana you can do a poison shot or strike here instead.
Now smoke your other poison wave or do something else blue if you don't have one, you're back in orchid spike, do blue red stuff for 12 seconds and return to the beginning of the rotation.
Doing this I reckon you could be in orchid spike state 2/3 of the time pretty easily, You're also briefly in green spike which you can make decent use of. Overall mana consumption of these isn't bad.
There's a build in here somewhere, probably with at least 15 alchemist levels, maybe even 20. Anyone care to try and spot it?
It probably involves light armor, since anything more would sacrifice evasion. That could be had as simply as burning a feat on it. Or it could take a splash from arty or bard or rogue.