Path of Exile is this game I am playing now, it just recently went into open beta, a sort of "soft release". Currently the game is unfinished but the existing content is well polished. Made by an indie New Zealand studio called Grinding Gear Games.
The best way to describe this game is it's like Diablo II but better. Or comparing to Diablo III- Path of Exile has more customisation in what potions you use than Diablo III has in total.
Best part is that this game is completely free to play, and will always be. There is a cash shop for aesthetic things, or you can even buy the ability to design a unique item for the game!
Lastly is the skill tree, more like the skill forest, or even skilldrasil. Hell the skill tree in this game would be comparable to my tree! Every class can use every skill, which are gems, and the tree allows you to buff the abilities you use. Link:
http://www.pathofexile.com/passive-skill-treeFinally here is a link for the main page:
http://www.pathofexile.com/