If the reason to back the project is the hope for the kind of writing one enjoys, then the team having writers one doesn't enjoy is, in my opinion, the best reason not to back it. After all, I have yet to meet a person who believes Planescape Torment was the most awesome game ever gameplay wise and needs a spiritual successor on those grounds. The word "doom" was of your choosing by the way. The question is whether we believe it is a project we personaly will enjoy - though maybe for you it's more a question of whether everyone else on the internet will share your taste
In general I feel Black Library has been loosing quality as a whole. And in my opinion the Slayer novels should never have gone past the original short stories that fit the characters - Games Workshop chose to milk the franchise for cash and Mr. Long is the person they paid to do so - a dirty job but someone has to do it, I'm sure. Still, I for one felt that there was a distinct drop in quality between the last Slayer novel written by King and the first written by Long.
Though my opinion is admittedly biased, as I am a fan of the old games workshop writers from the early days.