Well, I'm italian and I don't speak good italy... So any hostile mob isn't affected from potion effects. This is for the Lingering potions and the Splash potions.
Environment
Windows 10
Intel Celeron Processor N2820 (2.39Ghz)
Intel HD Graphics
4GB RAM
Java version: 8 Update 66
Comments 7
It's been over a year since the question was asked, please respond to the question or attach the files requests and keep the ticket updated.
So first sorry for my absence, I was so busy with school and my family. So I post here two gifs, where in the first you can see I used a poison potion on a cow and a skeleton. How you can see the cow suffers the damage, but the skeleton don't produces particles, so it doesn't is affected. In the second one, you can see i throw a speed potion and this time the skeleton produces particles as the cow do. I'm in the version 1.9, but I think you've already resolved this bug. So sorry for the eventual waste of time and thanks you for your help.
GIF: POISON EFFECT: http://imgur.com/3lLMQ5N
GIF: SPEED EFFECT: http://imgur.com/okfZD6K
Spiders, cave spiders, skeletons, zombies, zombie villagers, husks, wither skeletons, strays, withers, zombie pigman and ender dragons are not affected by poison.
Please provide some screenshots.