I find it funny to think the caps on Scrappers mean they can't take aggro....
Back in I8 an invul tanker had less survivability than many scrapper builds do now.
The Willpower Aura needs buffed, at least for Tankers and Brutes. The lame excuse for it "WP is too strong" is meaningless with the current state of IOs, Newer sets like Shield, Rad and Bio, etc.
The Dwarf Aura wouldn't need to be that good. Maybe as good as WP is now.
Leading back to the Kheldian Dwarf suggestion, since those are intended to hold Aggro on multiple foes.
Sort of the weakest of the 3 "tank" archetypes.
Right now they definitely are not #3 for the tank role. That would go to scrappers.
Because SR can easily softcap without it. Especially if you use both of the 3% def uniques.
I might use it while leveling, but tbh you could be softcapped for Melee in the 20s. SR also is essentially immune to def debuffs. And those slots could go elsewhere.
I would of course use it for any other secondary.