Re: 50th Anniversary Trailer Description
Of course it's eminently possible that 8, 8.5 and 9 fought in the Time War, were involved in various battles but that in one particular battle Hurt Doctor crossed the line, therefore it's one specific battle within the wider Time War, rather than the Time War as a whole.
My personal interpretation is that the Eighth Doctor was involved when the Time War began, and that he was trying to be good, indeed it could have been him who tried to save Davros from the Nightmare Child as mentioned in The Stolen Earth. Then when he regenerated and became Hurt, he could have become ruthless and decidedly un-Doctor like until eventually he regenerated becoming Eccleston who finally decided to bring the Time War to an end.
"Internet message boards aren't as funny today as they were ten years ago. I've stopped reading new posts." -The Simpsons 20th anniversary special.