I've just finished Torment for the second time (I don't think I've played it for 7-8 years, so it was nice to play again as I'd forgotten most of it. The ending still gave me a big lump in the throat).

Curious, though, as to who the red haired guy in the intro is - the one who is drowning and then you see him fighting against TNO. I know he saves Dakkon from drowning, but it's clearly not him in the intro. Anyone know?

I think it is just a random person one of the incarnations meet along the way, in the same manner as the girl in the same video.

I assumed the girl was Deionarra (although her ghost was prettier). You could be right though. He looked like one of the street thugs.