What does it do, exactly? From the skill planner, the descriptions makes it sound like a general version of Quick Parry, making enemies miss while you use a skill.
If so, then the skill is pretty godly when maxed , since you get a 55sec buff with a 100% chance of making enemy attacks miss when you're using a skill.
Indomitable Spirit lv10
Casting Time: 0.200 sec
Lasts for 55 seconds. Adds 100% chance of cancelling attacks while casting skills for the duration of this skill.
Casts a skill with a chance of ignoring attacks; cannot be dispelled for a set duration.