So I kept trying on my rogue and eventually managed to kill Sigryn. I had 15% Leech that for the most part kept me alive throughout the encounter.
I had a wipe at one point roughly 7 or so minutes into the encounter where all the bosses hard enraged.
I was pretty devastated by that at the time as it was the furthest I had gotten and one of the bosses (axe-throwing fella) had already died making the rest of the abilities significantly easier to deal with.
I realized after checking a guide that I should probably switch some talents around and focus almost exclusively on cleaving all 3 instead of leaving Sigryn blinded after interrupting Blood of the Father, and the extra damage from that is what got me through it.
Then I moved on to Unholy DK and got it within 3 tries. It was easy in Legion and it was still fairly easy now, even without much optimized gear, just due to the sheer amount of Dark Succor Death Strikes from all the imps you're killing.
I'll probably attempt either frost mage or windwalker monk next. I'm definitely leaving guardian druid and healing challenge for last.