yeah any level 10 build can take the boss with maxed out alchemy or arcana. they are basically godmode. To other people, it's fair game but to me i consider them cheese. That doesn't mean it isn't fun. Heck, even the solo potd build I posted uses maxed out arcana to take advantage of avenging storm.
You don't even need a party for the encounters you've posted. They are just all one meteor show/great maelstrom away from dying + withdraw to keep you alive. Or since you are running an alchemy build, Handmortar + stone joint (it's the most op alchemy potion) then use invisibility potion and wham wait for them to die.
I do know of a build who can solo the last boss + all the encounters you've listed without any cheese though and that's with level scaling mod from Nexus. So far no one has posted anything like it so that's good! Thinking of posting but I'm afraid it might get too popular and you know how Obsidian likes to nerf popular op stuff.
What is wrong with you people? You downloaded a mod from the Nexus. You obviously know they exist. Abilities in this game are literally text files you can edit with a simple text editor. You could just undo any of the unwanted changes to your build