Okay, let me see, let me see... how could this have been prevented without destroying the whole camp?
(I am not doing this out of spite... I use it to calm down; please no salt on this)
We could not sense anything with Thermal Control and they attacked out of the walls/ground. Any time we went near those, we had to dodge or eat the hit without knowing where exactly they were.
The overall plan would have been fine, seeing that it did work at first... but this incredible amount of damage was what stopped it from working.
Just so we are on the same page... these things have a Base Damage of 450.
Thunderbird, our most terrifying opponent so far, had 140 Base Damage and a Spell for 200.
These things outclass it in damage by almost three times as much, while being intangible...
How did no one notice them?
Granted, she could have taken a hit at full life, but only barely.
Now for the Shop... we could have bought one level of Armoured Soul, or one/two levels in a Spell, or three levels in A&O, but none of those would have made any difference. The latter does too little damage here, the former would not have stopped a second hit even if we started at full life and we finished off those guys fast enough as is.
In short... unless I missed something really important, this mission was impossible from the start. Unless we blasted everything, we would have died to a lucky hit or two anyway.
Please tell me what I missed, it bothers me...