I am just under 14 years late to this, but I will finsih running my Red Hand of Doom campaign for 5e and we will be going into RtToH afterwards. I have always wondered about this connection. Thank you!
Here's a thought - what would Hades make of Acererak / Lichdom / Orcus? I can't recall running into Hades as a deity / power in DnD aside from Deitieis and Demigods, but he has an outer plane in his name....
Take care all,
Ross