hello and welcome to destruction warlock mage tower detailed guide.
i know many of you will say that video is too long (40 minutes) but trust me if you really want the set its worth to watch because i grinded this boss for 20 hours not more not less and took me 147 attempts (with PVP Gear! if you have pve gear its way easier) also i have never done it on legion (i didnt play back then) and i was 10 hours in wondering why worm boss wouldnt lose the dmg reduction plates and then (holy) in the chat told me i had to do something different and it was mechanic and not random act. anyways i hope this guide will help you complete the challenge because lets be honest warlock set is best in whole mage tower sets for 9.1.5 patch. good luck and thanks for watching 
i tried it again today and after having the set already it felt way less stressful and i almost did it on 1st try