If you ask anyone who plays a fair degree of ARPGs, one of the issues with D4 (among things like itemization, boss fights, proper endgame) IS the skill tree. We have, effectively, less choices in the skill tree compared to the D3 rune system.
I want to play Puncture. Dump 5 points into it. Get the next one behind it and now, oh guys wait for it: Two choices! My god, I need to labor over this one. Choices choices choices.
The skill tree is bland, minimal choice, and frankly there arent enough skills in the game. There arent enough skills in the game to have tons of builds and playstyles. There just arent. And before you say "nah man you can choose tendrils or bone spear or minions or curse…yeah go ahead and make a build centered entirely around tendrils or curses. A lot of our skill choices are support skills, utility skills. Not the ones doing the damage. There are only a handful of damage centric skills and only a handful that are viable.
The skill tree, currently, needs to be tripled with choices. And I think Blizz should release a class-agnostic skill tree for everyone (not to POE size necessarily, but something everyone can spec into.) And it shouldnt be just +5 dex or +2% damage. Use the big boy brains and get creative.
Class agnostic tags: Projectiles, projectile size, Melee multistrike, melee arc radius, etc