He's done some goofy stuff fluff wise, but I think that's all he can really be blamed for.
GW as a company is the one that decided to have a rotation cycle measure in decades, demands more models be introduced, and even try to direct a lot the flow to what they think will be "Hip with all the cool cats down at the confectionary establisment"
But that's the problem with business in general. The higher ups become focused on numbers and keep sticking their fingers into the mix to try and help. It happens with comics, movies, and countless other projects.
So in summery, we will hate him.
Because he's the writer Warhammer deserves, but not the one it needs right now (We need 6th ed dammit)...and so we'll hate him, because he can take it. Because he's not a story teller. He's a fanboyish fluff writer, a maker of crunch...a Dark Kni...Wait who are we talking about again?.
"Snooki gives birth to Heavy Gun Drone squad, someone says they are over powered, then the world ends."