[Disclaimer: General consensus is that this is an underwhelming pool power. I get it. But bear with me a sec here...]
I'm trying out Corrosive Vial, and I'm not seeing the -DEF debuff in action. When I look in the combat logs, for example, using Brawl or Sands of Mu has the exact same to-hit chance reported against a target before and after it's standing in an active vial patch. My understanding of the power was that it was auto-hit for small DoT -AND- applied a ~15s -DEF debuff. (There's also no floaty debuff visual around the target mob, fwiw, even when the damage ticks are floating.)
Is there a better way to tell if the -DEF debuff is actually being applied?