Sorry to burst your bubble, but what you're asking for is 100% impossible.

A replay is not a video, but a play by play record of all of the game (this lets you do stuff a video can't like looking at the citadel, looking at what items people have bought, looking at skill trees, etc..

Let's say that there is a torchbearer is in this game you are trying to watch. A recent patch fixed his auto attack, so the replay will be different from what actually happened in the game, because when the game was played, every time the TB auto attacked in fire mode, the enemies didn't take damage. 

Discrepancies like this prevent replays from being viewed and prevent people from changing their critical game files and then playing online (prevents cheating but also causes modding troubles)

Well, you could record a video of a replay while the game is in the same version as the replay, but, that's kind of silly if you ask me.

The problem is that the replay feature in Demigod is incredibly buggy and poorly thought out IMO.

GPG won't fix any of this because they have no economic incentive to do so.