The worshiper requirements here exceed the population of Faerun lol.
I know everyone here talks about "multi-spheric deities" but is that concept even acknowledged by WoTC? I was the impression that the "Corellon/Bane/Moradin" of different settings are just recycled gods (but meant to be distinctly separate entities, i.e. core moradin and FR moradin are different gods altogether) and not actually meant to be the same being that occupies multiple spheres.
Nice thread necromancy - just got through rereading the whole thing!
I address your point about different versions of the same god in different settings here: http://www.enworld.org/showthread.php?t=252348&page=2#post4710334
With the benefit of more experience of 4e, I now know that as you say 4e does indeed take the Moocockian approach; the Bane of Forgotten Realms is not the same entity as the Bane of the core D&D world, and the death of one does not affect the other.
Re big populations of worshippers - in my core homebrew D&D campaign setting Ea, the same god can be worshipped on dozens of linked planes, allowing them to rack up very high Worship Point tallies. My player Upper_Krust adapted and expanded by WP system for his published 3e products, so that's what he's going with. Recently though I've been using dissasociated settings - killing Bane in my Forgotten Realms campaign would not kill Bane in my concurrent Wilderlands campaign, though I might well have an 'echo' of that defeat affect the Wilderlands version. Likewise Bane in my FR campaign is a very major deity, whereas in my Wilderlands game he's a relatively obscure deity of the dead Nerathi Empire. Zehir-Seth appears in both though as the evil god of snakes, magic and necromancy.