@Super:
We know it happened even though we didn't technically see it but it was very heavily hinted in that panel in the manga..
Derp derp
We never saw him on the brink of death.
Yes we did, he was on his knees coughing up blood, very clearly at the brink of death. Even more so since he was surrounded by Pacifistas and Doflamingo.
We saw him in grave danger. And later some doubts were expressed as to his fate by Mihawk and Perona.
They were not there, Mihawk left once Shanks showed up, Moria was killed by Doflamingo and Pacifistas after the official end of the war, they had no knowlage of that incident, their ignorance to the coverup proves absoulutly nothing in favor of Moria.
This is basic story telling. There's more to Moria's death than meets the eye.
Not really, the motives behind his death are pretty clean cut, he failed to kill Luffy, preformed pretty badly in the war; the Gorousei probably didn't see him fit to be a warlord anymore. Doflamingo even said he wasn't cut for it anymore and his orders were from a power higher than Sengoku. They couldn't just put him away in Impel down like they did with Croc, the place is a mess and probably isn't fit for any level six prisoner for quite a while, and I don't think the WG isn't above turning Moria into some sort of Pacifsta, so he could still be alive in the sense that Kuma is still alive.