| Caius Drusus Imperial DK (DC) Bragg Ironhand Orc Temp (DC) Neesha Stalks-Shadows Argonian NB (EP) Falidir Altmer Sorcr (AD) J'zharka Khajiit NB (AD) | Isabeau Runeseer Breton Sorc (DC) Fevassa Dunmer DK (EP) Manut Redguard Temp (AD) Tylera the Summoner Altmer Sorc (EP) Svari Snake-Blood Nord DK (AD) | Ashlyn D'Elyse Breton NB (EP) Filindria Bosmer Temp (DC) Vigbjorn the Wanderer Nord Warden (EP) Hrokki Winterborn Breton Warden (DC) Basks-in-the-Sunshine Argonian Temp | 
It does make me wonder, however, if the system/people in charge of curating endeavors are incorrectly counting this Void endeavor as "free" when it's really not. (As you pointed out, it's not reasonable to make people farm IA for one Void boss for a daily endeavor.) Today we only have two realistically "free" endeavors, since this one, the jewelrycrafting one, and the antiquities one all functionally require current access to paid DLC.
If they don't add Dro-m'Athra to Void creatures, they should at the very least look into why there aren't three (realistic) "free" options for endeavors today.
But that would mean that making this a "free" endeavor (by adding Dro-m'Athra or other base game mobs into the pool) would not necessarily change how many "free" vs. "paid" endeavors are offered in a given day. It would slightly increase the variety of free endeavors while slightly decreasing the variety of paid ones.
Necrotech_Master wrote: »there are a few non-paid areas where you can encounter void creatures, though its a bit RNG and there isnt many
one boss that can spawn is lady belain, which part of her fight she spawns some voidmothers that you can take down which count as void creatures (i havent specifically tested this with the endeavor, but voidmothers are counted as void creatures in other content)