Quick question. Imbiber glyph (damage when healthy) seems to increase attack power by a lot. Is it multiplicative and does it affect minions damage as well? Thanks 
No, it’s additive. Attack power does not matter whatsoever. It’s just a gimmick, really. Your actual damage isn’t proportional to that number.
I am gonna have to come back to you about that. I think the damage might be multiplicative, my target dummy testing were showing a flat 20-30% flat damage increase while using the glyph.
To be continued 
more testing later
I just did a quick test.
Imbiber increased my sheet attack power from 46400 to 48100. That’s an increase of 3.66% from 14.2% damage while healthy. My Ebonpiercer ticks only increased by 1.1%, however.
Thanks for the reply, I have done more testing and its additive like you said. The margin is large with minion, so I did an excel sheet with all the numbers and its not multiplicative