Masteries and 1- Pointers Passives like Warmth were all Passives and need to be moved to their own Passive Tree, or Talent Tree.
Which is what Diablo 4 is doing and it’s a step in the right direction.
As for Pre-reqs, they just need better utility. I understand there were some useless skills in D2 skill trees. These can easily be improved.
I think D3 actually solves this by separating Pre-reqs and Main Damage skills into Generators and Spenders.
Go back to D2 skills tree with this mechanic of Generators and Spender - You use Fire Bolt to generate Mana, then then Inferno or Meteor to spend Mana.
Now you actually need to put points into Firebolt because you’re gona be casting it quite a bit. It is Natural Synergy vs D2’s forced synergy mechanic.
D3 also limits total skills to 6. This is actually a good idea.
Go back to D2 Skills Trees with that in mind. No more putting 1 point into whole bunch of stuff and having 11 skills with a bunch of passives. It becomes condensed with a lot of trade-off and thus lot of build diversity. And remember your passive 1-pointers are getting more fleshed out in the Talent Tree.
So as you spec down the Skill Tree and unlock skills on it, you select your 6 skills that you will use. Each has a point-cap, and so you try to max them out.
Your skill points should be limited so that you are never fully able to max all of them.
Their limited nature makes them valuable.
The utility and differentiation of pre-reqs into Generators and main damage into Spenders, actually takes the D2 skill system and enhances with some good elements of D3. A hybridzation in this manner will make D4 skill system far superior than D2 and D3.
I actually never did that (except for MF builds).
I did look at guides to see what others were up to but mostly I just did my own thing. In D2, it was somewhat viable in hell.
In D3, I really wanted to play the Spirit Warrior, Witch Doctor (using all 6 spirit spells) but as much as I tried to make it work, it never did. Because I had no tools to make it work.
So the past 7 years, till now, I still want to make that Spirit Doctor build but there are still no tools for it.
If Devs add tools in Diablo 4 for players who just do their own thing, and allow us to do what we do at the higher levels (perhaps through crafting our own items), then that would be awesome.