I've talked about how much I like Adamant Will before, for allowing me to do objectives relatively unmolested thanks to the stun immunity, and arbitrator's stupid amounts of toughness regen letting me shrug most things off.
After some testing, Arbites Vigilant is actually kind of incredible (with BTL and dog). I thought that dropping my stacks would be annoying, but between being able to gain multiple stacks of Forceful in a single swing, and the dog also generating stacks, I tend to get back to full within the 3 second grace period on Adamant Will.
I'd love to also take Targets Acquired (the attack speed and cleave), but I unfortunately didn't have much more room in my build, and it was either this, or the +25% strength. The +25% strength seems to have it beat, out of all the testing I've done. I could theoretically afford it by dropping some nodes I don't strictly need, but I want them, and the 10% attack speed don't make a world of difference compared to Rebreather or Man and Cyber-Mastiff both letting me do objectives without giving a fuck.