A system of 'balance' where footing impacted your offensive and defensive abilities. Sometimes taking a hit is worth not being thrown off balance by a desperate dodge. Sometimes a series of rapid attacks to knock an opponent prone is more valuable than a single heavy HULK SMASH! swing.
PvP with /face as a standard for targeted opponents, balanced around circle strafing and clipping not being effective tactics, especially with the above factored in. Multiple factions instead of 2 sides so PvP is more dynamic.(DaoC influence duly noted)
Group dynamics do not rely on the tank/healer/dps paradigm. Instead, all players inherently produce positive aoe effects for nearby players and negative effects for nearby enemies. States other players put NPCs in allow you to combo your own abilities regardless of if you are grouped. The emphasis on combat is in working off of the actions of NPCs and Players around you from moment to moment.
I come across another player fighting on a pirate ship. I engage a ranged npc shooting at him, forcing the gunshot to go wild and hitting one of the melee npcs. Both aggro on me. The other player uses a distract/taunt to turn them back on her. I sweep the melee as it runs back towards her. She uses a leap attack on the now downed opponent to close on the ranged attacker. I combo off of the attack she used to close distance with me to buff her evasion and movement speed so she can cover the ground back towards where I originally saw her. She uses a rallying buff that gives me a temporary attack power bonus I use to finish off the ranged npc before following her up the boat.
Players have individual loot drops instead of competition. Base exp is given out equally to all players who contributed sufficiently to downing an npc. Bonus exp is given for successful combos, and more for multi-player combos.