There were only two ways of doing a new game: Keep the scripted camera with free movement or go for a behind/centered ala Witcher/TLoU/etc. There is a middle road variant like the Souls games where the player can keep adjusting the camera and move freely, but since GoW's action is more heavy that wouldn't work well.
All I'm saying here is that sure, it's been done before, but why not reserve judgment until the game can be played. AFAIK there hasn't been an all-out hack n slash from this perspective, so perhaps they'll be able to put an interesting twist on it.
The only game in this type of genre that worked as an over the shoulder brawler is God Hand. And it's control scheme owed more to Resident Evil 4 than anything else with the addition of dodging with the left analog stick; custom combos for combat variety. The only thing that comes close to second is Mad World (if you're locked-on or focused on to a single enemy) or No More Heroes (once again when locking on). Transformers: Devastation, Lollipop Chainsaw, and Killer Is Dead only go over-the-shoulder when using ranged weaponry. Otherwise they camera movement similar to Souls or Devil May Cry 4 or Bayonetta. Metal Gear Rising only went over-the-shoulder when in blade mode, performing a Zandastsu, or in forced scripted walking segments. No More Heroes 2 had this semi-awkward under-the-shoulder camera angle, if I'm describing it correctly. I have no idea why they decided to overhaul the camera on that one.
Reserving judgement can be said for any game, but there are times when you can tell when something is not right or not up to snuff. I said it before, was never a huge fan of Kratos or the God of War franchise, so it gives me less incentive to play. Had there been a completely new protagonist, then it would color me interested. I would have been hooping, hollering, doing back flips, and screaming like Daffy Duck in celebration. If there comes a time to play GoW IV, I'll give it a try, but odds are that I won't like it. You most likely would enjoy and a few others. but there is nothing wrong with that at all.