After a good 15ish tries in hardmode, finally beat the big bad guy. I managed to reach the 2nd life quite often, but there was always some stupid things happening. I wanna thanks little hornets trying to ram the immortal, or the enemy FV4005 ammoracking me from 1800 to 0 on a full life rack during the 2nd life of the boss. When that happen, you can feel fairness emanate from all around your tank.
So I'm not gonna lie, there is no magic secret that's gonna make you solo this mode. I was top 1 around 90% of the time, and it's really not hard to do so. Play Double, deposit Mirium and you're gonna be first and get juicy keys.
If I had to give my optimal team comp, I would go with 4 Double and 1 Hornet (To clean the Hedgehog). That being said, it's not gonna happen. You'll always have people playing Cerberus dealing 10k damage on the whole game. But you can at least do your part and pick Double, so you can be a useful member of the team. It has everything. Big gun, burst and most of all you can one shot most tanks with a turbo ram.
As for consumable, my go to was : Speed reload, healing zone and shield. The 2 first are pretty much mandatory on double, while the last one was mostly just a way to tank the sonic balls going at you in case you don't have ammo / teamates to clean them.
If your team is not composed of monkeys or Grenadier players, the first 3 phases should be a breeze. You might want to ping the map everytime you go to a new enemy spawn so the team stays together and doesn't split randomly.
During the first life of the boss, the team need to clear the adds until at least the last pop (Which is around 3k hp I think). It is in my opinion doable to just spam the boss without killing that last wave of life 1 in order to save a maximum of time for life 2.
For phase 2, you'll need to clear every single add before hitting the boss. Tell your allies in chat because they tend to forget within 0.3 seconds of entering the boss phase. Enemies are infinitely more OP than the boss, and they're the one that make you lose. Hulldown on some hill while you kill them if you must, but if you think that the enemy FV4005 is gonna let you live while you finish that last 4k of boss HP, it's not gonna happen.
If you manage to clear the adds of the 2nd life, you should have about 1 min 30 to 2 min to clear the last 3-4k hp. You need to make every shot count and I'm gonna give you the best (or worst) tip in order to do so. In the 3 wins I did against him (Med and hardmode), I used some stupid technique that actually seemed to be useful. Once there is no more adds, hopefully you'll have some Mirium left from said adds and the first 3 phases. If that's the case, Just go and hug the immortal from the front (When he is not doing the turbo). You'll take burn damages mitigated by Mirium, then mitigated by your shield. His weakspot will take pretty much your whole screen meaning you won't be able to miss it (Meaning if you go in with 2 shots charged, you should be expecting to deal between 4×400 up to 8×400 if you have the ammo reset / shield up). But in addition, it seems that hugging him also make him not want to move too much for some reason. When I did that during my hardmode win, he didn't move for a good 25 seconds, giving free shots to my team. If you have mirium + shield and some life, you can probably hug him for 25-30 seconds without much trouble, which you should do when the timer is sub 1 minute.
