At least I was able to make an OP build using coat. I do agree that though. Coat however used to be way more OP that it could proc too much but also affect more things than normal in a second. Prof rate nerf and coat nerf removed that which I was glad since coat was getting out of hand OP at one time. Still is very powerful but more an inconvenience now.
I mean coat helped me when I exploited effective+frozen before that stopped working. Also when fire used to be OP in arena back when I first done it , it was too good until perseverance makes Fire a lot weaker in dot DMG as well as bleed and dots in general. Of course poison included.
Coat with poison used to be very OP also when poison cloud could proc too many times instead of just once today for ridiculous DMG. If green garden wasn't even enough in being too OP to break the game , coat + poison sure was.