Once again, Chaos Marines compensate for their aging technology by allowing Chaos to bless it. That provides them with many advantages, many of which defy reality. There is a set of Chaos armor in Dawn of War II that in fact is said to grow stronger when struck by harmful blow, in it's description. Oh yeah, and Lord Eliphas the Inheritor's final talent in his Khornate specialization is to exude an aura of warp fire, so it's possible that Khorne's champions can get heat resistance.
Yeah. In some cases, however, Khorne's warriors attain a special enhancement called the 'Blessing of the Blood God', which among other things, gives a complete resistance to all psychic abilities. Correct me if I am wrong, but aren't Biotics psychically gifted individuals?
A point of great contention in the fluff itself. The point is this, Chaos Marines are immortal in the sense, that like most Marines, they did not age and will not die of disease or any other 'peaceful' means. Chaos Champions pretty much seek Immortality in two respects; never die from wounds, and be always remembered as mighty. You know, the whole 'song of my life told in many a gilded hall'.
Once again, their biological enhancements along with their daemonic resilience would provide them with admirable resistance against heat. In fact, as they are possibly partially daemonic, they have resistance against standard laser and slug weaponry, more so than regular Astartes. Also, Khorne's daemons are perhaps the second most attuned to fire, aside from those of Tzeentch. Bloodletters carry blades wreathed in flame, and Bloodthirsters have fiery whips. Azariah Kyras, a Khornate daemon, breathed fire in the climax of Dawn of War II: Retribution.
See the Blessing of the Blood God. Furthermore, it's not as if Khornate Warriors have no experience with psychic individuals. Psykers in 40K are infinitely more dangerous, in that their powers summon daemons, send forth balls of warpfire that can destroy on rushing battalions, they can form psychic storms that block travel through the warp. And the most potent can snap several hundred kilometre tall mechs with a lazy gesture. Don't know what a 'singularity' is, though. Barely ever played ME.