Just so you know HasBuffs only works with "And Buff Dura", and MissingBuffs only works with "Or Buff Dura". That's why you get the spam when you use it as HasBuffs and "Or Buff Dura <=", because these are not evaluated together, so it sees only "hey, I have these buffs, use this thing".
That's not to say it can't be somewhat modified to work this way with some effort, but I think dNh's solution is how I would approach it as well.
That's not to say it can't be somewhat modified to work this way with some effort, but I think dNh's solution is how I would approach it as well.