turn order is determined by Action Bar (yellow, with a number indicating your character Speed), set above your characters in battle. At level 20 (maximum) Action Bar consists of 200 points. Each minimal unit of in-game time (30 such units constitute “in-game second”) each character’s Action Bar increases by (Speed/10) points (this value isn’t rounded, thus 47 speed will give you 4.7 points, nothing is lost). When Action Bar is full, game transfers control to the player, he uses a skill, Action Bar is emptied and game continues.
Stun is a special effect, available on some skills, passives and gear, that directly decreases enemy Action Bar, delaying their turn. Stun is in % of damage dealt (more damage equals more stun) and gets reduced by stun resistance. Also, stun can’t reduce Action Bar below 0, so it’s useless to stun someone who just made his move.
Here’s some example – Rogue (50 speed) fights Warrior (40 speed).
Start of the fight – both have Action Bar at zero
20 units of time – Rogue have 100 points in Action Bar. Warrior got 80.
40 units of time – Rogue fills action bar and uses a skill. Warrior have 160 points.
50 units of time – Warrior fills action bar and uses a skill. Rogue is ahead of him at 50 points.
80 units of time – Rogue fills his bar again and uses another skill. Warrior have 120 points
100 units of time – Warrior gets his second turn. Rogue is at 100 points.
120 units of time – Third turn for Rogue. Warrior have 80 points.
150 units of time – Third turn for Warrior. Rogue is at 150 points already.
160 units of time – Fourth turn for Rogue. Warrior have only 40 points, he’s falling behind!
200 units of time – Fifth turn for Rogue, but only 4th turn for Warrior, advantage of a high speed!