I'm using Malmourral's mask for Annihilation marauder.

 

I'm looking at 3 sets:

 

The Victor, it heals you for 20% for a kill each 8 seconds.

 

Stationary Grit: 3% damage if you don't move, 10% armour if you do.

 

Descent of the Fearless: Gives Furious Power 10% damage bonus for 10 seconds like Bloodlust, just not group wide. Also dealing damage (Does it include DoTs?) has 10% chance of giving a stack every 5 seconds. Furious Power charges every 30 seconds by normal.

 

Which one I should use?

Descent of the fearless without question, it's an amazing set. Unless you are doing everything solo, that's a no contest.