I'm far enough along for the cultists stuff so that isn't an issue. With mercs I usually try to kill them whenever possible because they have a chance at dropping better loot. I am disappointed to hear that some sets are locked behind Oikos or Helix credits. I just won't ever get those I guess.
I'd probably have maybe 8 or 9 additional points if I didn't luck into some +fire dmg gear. I believe I'm at some +105% fire damage so it was worth it to dump the five points I could into it.
A couple of questions as I generally play isometric ARPGs.
Can you play as a ranged character only? It looks like there is a ranged skill tree based on screen shots above.
Are you able to respec?
I think you could try to be ranged only but it would very hard arrows are limited in what you can carry. You can craft them whenever.
I think you can respec by paying drachme.