Thermal Resistance components have no level requirement
 

..\Database\Items\ResistanceThermal.gdb

The line to enable the level requirement is commented out. I assume this is a bug because it is the only resistance type component that has no level requirement.

This means you can get 400+ thermal resistance at level 1 as long as you can support the power load. The damage absorption is still capped at 75% though.

Yeah, that was probably an accident. I've changed it back already, but I'm not sure there will be a Drox patch any time soon.