Atal'Dazar last boss on tyrannical

Hi, so I am not the biggest key player - this season I am maining a holy paladin and two days ago I attempted my first 20+ - tyrannical week (for most seasosn I usually stop at KSM, this season I am trying to do KSH) - Atal'Dazar.

The run went smooth - we had 2 deaths and like 8 minutes left when we got to the last boss. We then proceeded to wipe like 8 times and eventually disbanded. The same thing happened day later in 19+ - smooth sailing to the last boss and then like 10 wipes and disband. I will say that there was no toxicity in either of those runs, which was nice.

Could I get some help on the last boss - recommended tactics? It seems pretty straightforward - stay stacked, heal trough wrecking pain, run out with soulrend, nuke adds and move back in. The spiders however always get ot of hand and eventually - since the fight can be quite long - you step on a spider (most ppl do). Is there any trick to keeping them stacked or something I am missing? The only thing i started doing in the 19+ is that towards the end of fight, when there is a lot of spiders I pop bubble and try to clear some of them.