Dopplers are balanced pretty well, but sadly the game has too less of them.. theres only 1 single freakign doppler in the whole game and this its naturalyl linked also to 1 unique sword schematic and its unique decoction, which must have been naturally designed so in this game, that you ca't get both, cause for one you need to kil lthat doppelr, for the other you need to let it live ... / so super annoying....
There should be another doppler in the game with that you have no problems of killing it, because killing the one in that quest feels wrong and gets you as reward for doing practicalyl the right thing the schematic for the gnomish gwyhyr lvl42 sword thats one of the best swords in the game so far.
there should be also a doppler somewhere that you just kill to get its decoction, so that when you make the right decision at that other quest you can have both, the decoction and the sword schematic fpr the gnomish gwyhyr. As long as that gets not fixed, I won't play the doppler contract quest.