Don't use that. Look up a skill in the support tree, it's called gaurd. You need to keep it on both bars. Use that. Build super tanky and get a friend To make a supper damage oriented build.
I tried once. Idea was to have my PvE tank character somewhat useful.
Never seemed to do much. The Vanguard's Challenge gives a little health and healing taken, but it really needs Armor or super buffed regen for tank use.
Best use case appears to be as a support character to ranged taunt "busy" enemies and keep yourself out of LoS/reach as much as possible simply to nerf their dps them from afar.
If you're up there next to them and you're taking 35% extra damage, even a super tanky build becomes very close to 'regular tanky' and you die.