A couple of cultists from Dragonborn are still outside my house in Whiterun. I had to drag them away because everyone kept stopping to comment on what should be decomposing corpses at this point.

I think one or both of them is still there, and it's been an obscene amount of time, ingame AND out.

Thoughts?

Try staying about of town for at least 10 in-game days. It may take an absence of 30 days, but they should disappear.

It's Whiterun, the most convenient city there is besides Riften. (For my playstyle anyway).

Eh. We'll see.

Ok. So, you frequent it a lot?

This is just the way the game mechanics works. Each cell is set to a respawn timer. Some are set to never respawn, while others are usually set to 10-30 in-game days. If you frequent an area often, it resets the respawn timer and it will never respawn.

Corpses being cleared are set to various triggers. The cell respawn timer is a good way to ensure they are cleaned up.