HOW TO DO IT WITHOUT DRUID AND AVOID BUG
So I recently just did this with a friend and we were able to do it just fine after figuring out how to get passed the bug and not have a druid.
For Reference he was playing DK and I was playing a warrior so technically it is definitely possible without a druid but ofc a druid makes it 3x easier.
First, make sure the raid is on Normal.
Next, make sure you take off all your gear to avoid killing the boss. This can depend on how much base dmg you do.
Before starting the fight communicate who will be entering the construct and who will be kiting the adds that spawn. Reason why I say this is because both jobs are equally as important to make sure the boss doesnt bug.
Whoever is entering the construct, follow these instructions so that its easier and efficient for you bc if done correctly you can do it in one try:
FIRST, Have the stopwatch ready. You need this.
SECOND, Once Socrethar comes out of the mech for the first time start the stopwatch and get in the construct! Dont wait to start the watch once your in mech,NO, start it as soon as you see him come out of the mech.
The purpose for the stopwatch is the following: Every 30 seconds after socrethar abandons his mech 6 souls will spawn in the blue portal. So the stopwatch will work as a indicator of when to pre fire FEL PRISON directly on the blue portal. So keep an eye on the stopwatch and cast FEL PRISON about 4 seconds before the next 30 second mark.
ex. before 1:30 gets to 2:00 cast Fel Prison at 1:56 or 1:55 to play it safe.
Make sure to cast FEL PRISON close or right on top of the blue portal so that its easier to manage. And keep track of your stopwatch bc the timing is what you have to trust. Trusting those 30 secs will get you the achievement.
OKAY STAY WITH ME ALMOST DONE.
That being said the person that enters the construct needs to also be looking at his constructs health bar. Reason for this is bc if your kicked out of the construct it will bug the boss as we all know. TO AVOID THIS, make sure you stand close or literally right on top of socrethar while in the construct so in the case where your kicked out earlier thats how to avoid the boss bugging.
Now if done right the only time you will be kicked out of the construct would be when all 4 waves of souls are already in the fel prison. Meaning,by the time your stopwatch shows 2 minutes you should have 24 souls in the fel prison. At that point your constructs health should be at like 20%.
Once you know the 24 souls are there have your duo nuke them. DISCLAIMER: Make sure your duo destroys the fel prison first and then the souls. The souls will not die if the prison isn’t destroyed first. But chances are they will die instantly anyways but just letting you know just in case.
DUO PERSON: while all the above is happening your job is to kite the adds that spawn in the other portals. And then nuke the souls when your told to. If you have a AoE it would be easier too that way you literally nuke them. Be careful not to kill the boss by accident.
Once you kill the souls just kill socrethar and achievement is yours.
In my experience I was able to do this in one try, of course it took us hours to figure it out but once we did it worked perfect. Trust your stopwatch and your timing. Make sure your focused and no distractions. Those 2 minutes are extremely valuable bc if you mess up the timing your gonna scatter the souls and then good luck dieing if your a max level character. Even with all my gear off it took a while for the boss to kill me on Heroic, and that’s bc I didn’t die in Normal so I wouldn’t know. Messing up the timing will put you more at risk of bugging the boss and killing him too bc there will be a lot going on.
I hope this will help all who have been stuck on this achievement. Good Luck!