No true damage after first hit from hitting Rift Herald from behind. No 5 devourer stacks for assist

I just tried to duo it with my top laner Malphite today while I was playing Master Yi and had the devourer jungle item. (On my other account Maikal of Rngsus)

The eye stayed open like it's supposed to since I have the jungle item, but after the first hit, the eye stayed open but I did 0 true damage. As you can imagine, this made killing it much more difficult than it was in the patch previously, even though this patch intended to make the Rift Herald weaker.

Also, it does not give 5 devourer stacks for assisting to kill it like all epic monsters are meant to. It only gives 5 stacks if you kill it, and 1 if you assist, but if you click away briefly so that you pass the buff to someone else, you don't get any stacks. I haven't seen this in the bug fixes section of the patch notes so I'll assume it hasn't been fixed or acknowledged.