Decaying Hex doesn't count as a source of Spell Damage over Time

Like title says.

Decaying Hex, despite being a non-ailment Chaos Damage over Time debuff applied by a spell (a curse), does not have the Spell Tag and so does not count as a source of Spell DoT for supports like Swift Affliction and Chaotic Freeze.

I classify this as a bug for two reasons:
First, it severely limits Decaying Hex's usefulness since none of the available Damage over Time supports can work with it. In my particular case, it means I don't have any reliable way to apply Chaotic Freeze for my Acolyte Chaos/Freeze monk.
Second, and more directly, Decaying Hex supports a Curse Spell, causing it to "inflict Decay, dealing... Chaos Damage per second". That is, Decay is a non-ailment Chaos Damage over Time debuff being applied by a Spell. That is, the DoT from Decay is non-ailment Spell Chaos Damage over Time. QED.

(I get this could cause a problem with Blasphemy; simple fix would be to add the line "Modifiers to Curse Effect apply to debuff's Damage over Time", add the line "Debuff deals x% less Damage over Time if supported skill is cast as an Aura", or both.)

Also, while I'm here, Impending Doom has the exact opposite problem, where it can support Blasphemy'd curses despite not actually working with them.