I managed to kill all three of these prototypes in era with a six box crew. To say it was quite a task is an understatement. I would like to share my knowledge for future boxers looking for a challenge. Note: I do not use any software assistance.
Elemental/Time geared Paladin, with cleric, druid, bard, shaman and ranger or mage (I swapped out after the first fight). All with 150+ AAs and pretty solidly equipped for group gear on the boxes.
First, it helps to know what order they banish (IX to X, X to XI, and XI to IX) so that when you down the first one, the second you can ensure you get banished to an empty room. To be honest, I'm not sure how I did it. The first one I started with was X and maybe that was part of the key? It was banishing me quite often and trying to run back when snared (sometimes) and being beaten on by an unslowed prototype was difficult. However, part way through, it started summoning immediately after banishing. Did I get lucky? I'm not sure. Perhaps I had enough aggro with my tank that it hated me enough even though I was far away.
The other kills were almost as hard because the Oil Spray made it so that it was difficult to get back to the prototype before it banished someone else (and the longer I was away, the longer it beat on a more squishy opponent). Trying to move two characters was quite difficult and obviously lowered DPS. I eventually tried to time my radiant curies (shaman/druid/cleric) to get rid of the snare before I was banished. Just as importantly, I left my first few buff slots open and would annul magic on myself if I was banished with the snare. That combined with my Holy Steed allowed me to get back fairly fast.
The mob was a bit resistant but the fight was so hectic I couldn't really tell to what extent. Many of my stuns were resisted. Slow definitely took a few tries even with Malos on, but a number of dots did land.
I really recommend having potions on your characters and using them. The prototype's melee DPS isn't super high but it's enough to hurt a good bit if unslowed (plus at least one flurries and another occasionally wild rampages).
Because of the banishes, it was hard to get an accurate HP count, but I'd say it's close to 100K. The mobs did have MOTM 5 on them, so no pet tanking. Max hit was low 500s. I never actually saw the listed fire AE go off and there's no record of it in my logs.