Too many staff is the reason it's taken them 12 years to develop Diablo III? It's the reason the PVE raid and non-raid content past T11 in WoW was absolutely anemic / non-existant for the life of this entire expansion? Because they had too many people working on it. Of course.
See my other post please.... About how legal people and marketing people affect development time (TLDR: They don't)
Also Diablo 3 hasn't been in development for 12 year but thank you try again.