Decaying Hex & Impending Doom Not Working Properly?

I'm not sure if the Decaying Hex and Impending Doom Support Gems are not working properly or if their tooltips are just misleading, see Support Gem images below.





Because Decaying Hex's tooltip says "Supports Curse skills" and Impending Doom says "Supports Curse skills that you cast yourself", we are led to believe that Decaying Hex should be able to be applied to curses that are attached to Blasphemy, Hand of Chayula, etc. At the same time, it would be fair to assume that Impending Doom would not apply to curses attached to Blasphemy, Hand of Chayula, etc.

However, I have tried using Decaying Hex with both Blasphemy and Hand of Chayula, and have not been able to apply Decaying Hex to enemies via those methods. Conversely, when I tested Impending Doom with Hand of Chayula, Doom blast would trigger when the attached curse expired. (Doom Blast only triggered sometimes when the curse expired due to an enemy being slain.) This interaction was unexpected as I was not casting the curse myself.

It seems to me that either the tooltips or the Support Gem interactions need to be fixed. Is anyone else having this issue?