There's a whole bunch of aggressive ottuk to the south (that can't drop a heart) amongst the neutral ottuks (that can drop the heart).
I also had to kill 10 of the neutral (innocent+cute) ones before it even dropped...
and now I feel really crappy, as ottuks are ace! I always feel bad when I have to kill cute innocent creatures ingame that're just going about their day, living their life hurting no one... :( (not real, I know...)
(and no one seems to know how to tame them yet either...)
(UPDATE EDIT: they're tameable after getting Iskarra renown rep high enough and doing a little questline that super doesn't tug on one's heartstrings! :'( )
I wouldn't have minded quite as much had the hostile ones attacked me and dropped a heart...
That said... 9 of them didn't have a heart at all... so maybe they're not quite as cute+innocent as I believe? :S
Also of note, this is a single solitary side quest, no follow up as far as I could see...
and everything else on the list required multiple kills too, before dropping their 1 singular required item..
And like the VLDL video a couple weeks back (mentioned in another comment), this was exactly the same... although surprisingly I didn't find any furniture inside any of them :P
(2nd UPDATE: now that Midnight has launched with player housing... I'm actually able to find some furniture sometimes on (in?) corpses these days! :D ... but not these ones, probably... I haven't checked :P )