I can see two scenarios here:
1) It was simply a bug that shouldnt have happend - that wouldnt require nerfing the fight but fixing that bug
2) If two of the adds touch and one consumes the other one the one that remains gets huge buffs - more HP, more defense, regen... I dont remember all of them. Its getting really, really difficult to kill it at that point, which is why you always want to make sure to keep them apart from each other. If thats what happend: You failed a mechanic and got punished for that. You can wipe in level 60 content if you dont do mechanics correctly aswell - why should they be removed in any content thats below 60? Should we remove mechanics in Sastasha too?
-> after a timer runs out, Kalia will cast "nerve gas" (...or was it nerve cloud...), another mechanic that deals damage based on how much HP the adds have left still (if you havent killed all of them, it used to be an insta-wipe) and puts a vul-stack on everyone. (We used to deal with this by shielding everyone) - so if thats what happend: its supposed to be a dps-check, not an insta-wipe. You can now survive that, if you fail to make the DPS-check.
What do you mean with "locked up the entire instance"? I dont really understand what thats supposed to mean? Did it stay sealed even after you wiped or what? Did the boss freeze and didnt do anything anymore? If you just couldnt kill the remaining add - well, to bad for failing a mechanic. Sorry to break it to you: Not everything is faceroll easy - and it shouldnt be.
I hope you dont mind me saying this but you dont seem to have the mind of someone who should raid - you failed a mechanic and your approach isnt "Okay, we wiped, why did that happen and how can we avoid it the next time? What did we do wrong? How are we supposed to handle this?" but instead its "OMG WE COULDNT FACEROLL! NERF! NERF!"
If you cant handle a challenge and mechanics: Stay out of content that is challenge and mechanics.