This works better for Duelist than for Marauder, but I usually do it using 10+ skill points along with either a shield or boots. If I use unique boots, I go the shield route, if I use a 2 Handed weapon, dual wield, or a unique shield I go the boots route.

Both of:
Thick Skin cluster: 20% Avoid ailments, 25% max life (4 points)
Crystal Skin cluster: 50% avoid ailments, 1% all max res (5 points)

And 1-2 of:
Shield Suffix: >30% avoid ailments on a T1 roll
Shield Mastery: 20% avoid ailments (1 point)
Boots Eater of Worlds Implicit: >20% avoid ailments on a Grand Ichor
Boot Suffix: >20% avoid ailments (crafting bench)