I have EBOTD, but when the Act 2 mercenary tries to hit the immune council minion, it's awful and I have to go and kill him myself (which I prefer to avoid). On the other hand, with the Act 5 merc, he easily takes down half his health. My main problem is that I hate phys immune council minion, I thought that using protector stone and renewed bone break would solve that. But I'm going to follow your advice, since you know more than I do and have already tested the ideas that I've just come up with lol
You can zerk it yourself w/grief Mainhand
Or use dreadfang zerk to trigger amp for merc, or dual Dreadfang w/frenzy