I've argued against decapitations before: it's simply not realistic. Decapitation is difficult enough when the victim is bound and has his head on the block: until the invention of the guillotine it often took multiple tries. In face-to-face combat, that's just not feasible; and not practical either. You don't need to split the vertebra to kill someone: severing the throat arteries is quite sufficient, and a lot easier. There's no reason to go for the back of the neck.

Dismemberment is possible with axes and heavy chopping swords, but I don't think it was that common. The shield was the cheapest and most common piece of defensive equipment, and a shielded opponent would only expose his weapon arm when striking. It's also difficult to make these animations look anything but schlocky, so I doubt the team will bother with it.