ToME: the Tales of Maj'Eyal

Found troll-hide drakeskin leather armour of the wind. It's either made of dragon or of troll, not both ;).

troll skin strapped on dragon hide

It's a cheap imitation of dragon leather made out of troll hide. Those sneaky dwarves!

Well, lets get technical here. Troll hide is a prefix ego, which gives regen, and drakeskin is a material tier.

2 Easy solutions, remove the option for drakeskin to get troll-hide, or rename troll-hide to something else. Like Troll-blood covered drakeskin leather.

I don't see why you're so shocked. Dragons' amazing fecundity is well-documented, and it's not like trolls have high standards.