Death's Dance

I Had a few custom games to see if it's true or just a coincidence, I'm talking the "damage reduction" from Death's Dance

> Stores 12% of all physical and magical damage received, and is taken as a damage over time instead, dealing one-third of the stored damage every second.<

and it's interaction with refresh (full or partial) and effects of on-kill abilities (Irelia's Q, Annie's Q, Hecarim's Q), i don't know if it's intended but the damage received as a DoT from that ability, even if the Dot would kill the target, won't refresh the skill or activate the effect it should've had on instant kill (Nasus's Q, Mordekaiser's Q, Olaf's E, Gankplank's Q etc.).

Is it a bug, or is it intended to be like this?