A Question About SotW (Not a Rant, An Honest Question)

[WhateverUSMC]

Again, I'm not a beginner, but this area is labeled 'Questions', so here goes...

A couple of days ago (sorry, don't remember which day), I was on my warlock, running towards Samal, and a hunter popped up, and went into SotW (sorry, I don't remember which hunter). I had just woken up, and wasn't paying attension at first, so I cast Ivy on the hunter.

It landed.

I ended up dead, in part due to my surprise over Ivy having worked. Given SotW's high resistance rate (I didn't look up the number, but I'm pretty sure it's a big number), is this a bug, or just a numbers fluke? Nothing else I have ever casted on a SotW'd hunter has ever worked, so I'm curious what's up with this.

Thanks in advance.