Jamba has an attempt to warn about an Inactive debuff. You can find in it Jamba-Toon under warnings. I don't PVP, so I have never tested it. However some have said it does not work. You could try. I might have the name of the buff to check for wrong, but you could open up the Jamba Toon locale and change the line where it says L["Inactive"] = true to L["Inactive"] = "the proper name of the buff".

Jamba-Proc shouldn't be able to detect buffs; so you Proc idea won't work, although if it does work, I'd like to know.