it is pretty much straight action, with some light RPG elements (skill tree). and yeah, the combat is pretty much an Arkham game with swords (but luckily unlike Batman, the main character does not have a "no kill" policy). it also has a 'parkour' system much like the Ass Creed games. plus throw some Far Cry 3 fukkery in the mix (release a caged beast in the middle of an enemy camp, and watch the chaos)
but where it really shines, and becomes more than the sum of it's parts, is the "nemesis system". basically there's this whole WWE orc soap-opera that plays out with the orc "captains", and their interactions with you. if some no-name kills you, he will be promoted to captain. if a captain kills you, he will become a more powerful captain. and the next time you meet them (I don't wanna spoil much, but you dying and coming back is part of the game), they will talk some shyt like "I thought I killed you last time. lemme make sure you stay dead this time". if you run from them, they'll call you out for that too. if you think you kill one of the captains, but don't decapitate him, there's a chance he'll come back with a crazy scar, on some "you left me for dead" shyt. all in all it makes the game very engaging. it will really make you feel some sort of way seeing these dudes rank up when they kill you, or finally getting revenge on a shyt-talking captain that killed you
it's also very dynamic, so no two players are gonna have the same experience. that combined with the 'open world' aspect makes it so you might end up in some very crazy, and possibly unfair, situations. it's one of the few games where 'running away' really feels like a legit strategy. and again, part of that is knowing that if you die, and bunch of orcs are gonna come up. the nemesis system really does add a whole new dimension to the game, and I'm sure we'll see it copied in many future games (ironic I guess, since this game borrows from so many other games)