EDIT: can confirm, if you kill all horde enemies with 1 spell/attack spawned ones will be level 1, killing your exp. bad stuff Especially if you prepare on kills usually (doing some weak/vulnerable, using zod rune, then doing massive damage to cull all at once)
BUT amount of mats/loot seems to be unaffected by that bug, only exp.
***Also on a side note, shoudnt Elf Barbarians Hate prevent on-death effects from the horde? I mean i explicitly carry this one with me to avoid wights ressurections/guys with sacrifice to the light, now we have that crappolano seems unavoidable
***ALSO is there any particular reason why we cant extract from nemesis? 90% of time they spawn from my own charm and i cant extract cores from them seems not too logical