At what level can an AD&D fighter without any magic items detect secret doors just by walking past them, see in the dark, and live for a thousand years? 1st, if he's an elf. The idea of different species having superhuman powers as a baseline before we even touch character levels isn't exactly a new one for D&D.
And at what level can an AD&D human fighter start to detect invisible foes, without any magic items? 8th, if his Intelligence is high enough. 13th for even the dumbest.
I'm not comparing mid or high-level AD&D characters to Thor on power level; just pointing out that the vibe of AD&D characters who survived for a few levels could rapidly start to get more Asgardian than Dragonslayer.