What's wrong with Grim Dawn's skill system? Or Titan Quest's for that matter.
Skills aren't limited by your level which means you can quickly go for high end skill max it out before you even kill warden. Aka making game easy as shit. It only changes in late game where game catches up to it but by then you already probably have gear to outmatch it again. With GD i have to play on veteran mode to have any kind of semblance of challenge as game catches up faster than in normal mode.
I started to play with artificial limit to mastery (only upping mastery to char lvl) and you could see it was much better game this way. Before you max out skill game already catches to you and you naturally progress into gear upgrade and slowly build up power, bosses and encounters then make a lot of sense and pose actually a challenge.
Overall i like GD skill system but this nugget just annihilates much of game gameplay. This isn't particularly only GD problem as challenge of campaign seems to be going away in many arpgs who started to treat it as 20-40hours opening to their end game which usually i don't really like.