They currently aren't worth doing for the following reasons:
1. Very hard
2. Little loot
3. Not deep enough for radiant fire crystals
I got 3 simple ideas that can help with this problem:
1. Make it like the Grinchlin Assault's final treasure room that has a single box in the middle that has a chance to contain a gear piece matching the theme of the mission. For example...
C42: Vile Striker, Ash of Agni, Deadly Virtulisk Mask, etc...
GitM: Volt Driver, Volcanic Plate Mail,Grey Owlite Shield, etc...
HoI: Glacius, Wild Hunting Blade, Mega Magnus, etc...
And so on...