So basically you can start off with this new ability and apply the debuff to 5 enemies. You gain pretty much 5 bonus turns, as you can hit each of them once and then assuming you're running Palp lead, you can aoe which will give you another turn as long as the enemy doesn't resist a ton of DOTs, so that will be 6 turns taken + 1 after you first use the ability, so totally 7 turns for Vader before somebody else can move. Which means you will have only 2 turns left on Merciless after that, which means every 2 turns Vader will be able to take the total of 7 turns without anyone interfering o.O.