In PvP, use on an enemy to either disable a skill or force the character to stop using skills until Diversion expires or is removed. This can be timed to try to force monks into a bad situation during a spike.
Instant recharge effects, such as that from Glyph of Renewal, will cause a skill to recharge instantly even if it was completed while hexed by Diversion.
Assassin attack skills used out of order have an instant recharge effect and can be used to get rid of Diversion with no adverse effect.
Diversion takes effect immediately when a skill finishes casting, before the skill's effect takes place. This means that if the hexed foe uses a hex removal skill, Diversion will be triggered by that skill, disabling it and then the skill will remove the next hex.