I have designed a skilltree system for an upcoming game proposal. I'm exited about it because it solves an innate problem of the basic skilltree design, namely the fact that players end up investing all of their skillpoints in the best/most powerful skills. To do that they would either hoard their skillpoints while they level up or simply respec when they reach a skill higher up the tree (if respec is an option in the game). This problem has proved to be a tough nut to crack and as far as I know there has been no satisfactory solution implemented in an existing game. I could be wrong about that ofcourse and therefore I made this topic. 

I would like to know if someone knows of an existing game with a skilltree system that solves the problem I mentioned. I'm not looking for a mix&match kind of skill system, it has to be a system like the classic skilltree system that was introduced in Diablo2 if I'm correct. 

I remember a tiered system. I think it was in "forsaken world", but it may have been a different game.

Basically each skilltree has a set of tiers, and you need to spend a certain amount of points in a tree before you have access to the higher tiers.

The high level skills are in the high tiers, the low level skill sare in the low tiers.

Its up to you where you put your points in the low tiers but you have to put them somewhere.

A vertical bar would show on the side showing how many skillpoints had been spent on the tree and once it reached the height of a higher level skill tier you were allowed to buy skills from that higher tier in that skilltree that you met the prerequisites for.

I think the standard design for most skilltrees is that you need to unlock prerequisite skills to progress through the tree, so that prevents hoarding points. Maybe I'm not following your question so correct me if I'm missing the point, but I think most modern games with skilltrees use this idea. Payday 2 is probably the last game I remember playing that uses this.

Ori and the Blind Forest uses a simple solution for that.

Like other games, it is tiered.

"Skill Trees" are just "Research Trees" applied to an individual units.  "Research Trees" come from "Tech Blocks", which come from Avalon Hill;-)

Most aspects of "complex games" are many decades older than most believe them too be.

EDIT: If any "historians" out there are interested in knowing this...  Avalon Hill's "Tech Blocks" began as an internal thing where they made a "Tech Tree" covering the introduction of every relevant piece of equipment and gun that was available during WWII.  They used this as a reference document for all of their games.  They eventually began using it, in limited ways, within some of their later games.  Sid Meier played board games, and brought this concept to computer games in the form you know it with Civilization.  He got it from the board game Civilization, which wasn't actually a very good game, and train games which just naturally had a similar aspect too them.