Infernalist offense feels bad.

Been checking out the witch class this season as I dont really do casters all that often but in a game that plays like a bullet hell it felt right to try and play the evade and fire route. I am disappointed. Reading through the potential passives for the witch shows a huge lack of fire nodes, really the whole passive tree has a distinct lack of these nodes, and the ones the exist are primarily boost fire damage or boost ailment. Both sound great but dont really feel good when playing against anything that has even a hint of resistance. Ive only done the fist trial currently and each of the options Ive tried are pretty bad too for my current state of the game. Unlimited mana, everything contributes to flammability, stat boosts, and demon form. Maybe theyre great later but they dont feel as impactful as anything the warrior, monk, or huntress had.
Basically I think the passive tree needs to be changed somewhat to allow more freedom in building as being locked into a summoner when I would rather embrace the pyromancy is awful. I shouldnt have to buy, find, or craft a legendary item to force viability on the build that would otherwise not work either.

Demonform. Get some fire penetration, there are a few nodes right near the witch starting area. Also, get the curse that lowers elemental resistances and use it on bosses or rares that are beefy. Increase the curse duration and lower its activation time.

You need to use several different fire skills in order to make this work and you can put fire penetration on whatever one you use to kill tougher mobs for a nice damage boost. Just between that starting node and 1 fire penetration gem you're looking at almost -60% resistances. Once you get fire pen level 2 you can just forget the curse entirely and run something defensive like temporal chains or enfeeble on blasphemy.

I am currently using fireball, incinerate, living bomb, and ember fussilade. Fireball is for clearing, living bomb for infusions, fusillade for murdering tougher mobs (fire pen), and incinerate for fun.

I just refunded all the fire nodes and took darkflame and chaos nodes. Much of what you mentioned was indeed what I was doing minus incinerate cause it didnt work without actually spending mana, though I did try it with mana so it would work and was unimpressed. Maybe it works, but I think it should be more accessible than it is. Having more nodes that impact each element individually would be best imo but having generic elemental pen/strength would be fine too. Also on a side note why the heck doesnt the firewalker node actually add trails of flaming ground to your character? Its just silly that it doesnt work like that.

I'm not sure but that sounds like a cool idea. I have not played with chaos conversion yet but plan on giving that a try as well, as others appear to be having success with it.

So far so good, I dont have any great modifiers on my equipment but its doing well in act 4. Thats not to say Im shredding bosses or wiping the screen but at this point I think Ive figured out how to play this cobbled together build. :P