Path of Exile is currently in OB state, I must say that this is one of the best action rpg I played, this game totally beats D3 hands down, there is no cash shop, only micro transactions.
"Skill tree" what am I saying SKILL FOREST is unique, you have total control over your skills and passive's.
Gem system instead of linear skill system, in Path of Exile active skills are are itemized onto "Skill Gems". These gems confer an active skill to
the player when they are socketed into equipment and gain experience as
the player slays enemies.(info taken from PoE website).
6 Character classes
Marauder : Bulky fighter, can be built as tank, or DD (best starter class, imho)
Templar : Hybrid between magic and melee, can be built as a tank, mage, or hybrid with powerful self buffs.
Witch : A mage with powerful magic spells, can be built as a support or straight nuker
Shadow : A Dexterity INT hybrid, I have no experience playing this character, but mostly I've seen him built as pure glass cannon with some defenses or the other way round, with staff and shield
Duelist : Dex, STR hybrid, I've mostly seen duelist players go full DPS, and wrecking stuff while dual-wielding
Ranger : Archer class using Bow, traps, and self buffs
You can build your character however you want, you can build a Bow Marauder.
Every character can utilize buffs, they are not locked to specific class or build.
Tons of event's everyday and much more to try. I haven't gotten far yet I am only on Act 1 but I am gonna finish it soon
I haven't tried PoE pvp system YET, but I heard it's lots of fun.