Why did I mark this as 'sad'?
Want a farmer
Don't have any characters to 50 yet
Unfamiliar with Invention Origin enhancements
Not a lot of influence
Nothing wrong with any of that.
It makes me sad that it is the expectation vs "I'm gonna go rescue someone", "rob a bank" or "smash some snakes". There are 100s maybe 1000s of hours of content in the game pre level 50.
"that's actually decent playing the rest of the game as well" - Try some out. You'll discover what play style you prefer and go from there.
Spines/fire brutes are not the absolute best character, farmer or earner. Fire/ tankers maybe even less so. My earner is a level 33 single target focused character.