What I said about combat was more for the purposes of a bon mot at Bioware's expense than anything else. I share your concerns. I've said similar things on this forum before. What CDPR is trying to do is very hard, and it hasn't really been done before. The best attempt I can think of is Gothic 2 or maybe Fallout NV, but those are very different RPGs from TW1&2. Personally, I would have preferred something with the production values of TW2 but the size of TW1 or bigger. To me, the Open World promise of Do Anything (and also Be Anyone--which doesn't apply here) aren't what I look for in an RPG. They're nice if they're there, but I really look for C&C and storytelling more than anything else.It's actually not that easy. Most of the quest design flaws in games like DAI and Skyrim are not there because the devs couldn't come up with something better or because they specifically decided to offer such content - it's there because it's a side effect of offering a huge open world. So offering a huge open world was the specific desicion and not offering bland side quests. That's just a side effect of that first decision and something that is often a result of time and money constraints which themselves result from that first decision.
So it's indeed a completely different question whether we talk about quest design and combat. Combat isn't really connected to any other game mechanic or system. You could give Witcher 3 a turn-based tactical combat system, a system based on cards or an action system like we expect - it wouldn't change much of the rest of the game and there isn't really a prerequisite for your combat decision (apart from your input hardware and the possiblities arising from it).
Quest design on the other side is deeply connected with the overall narrative, with world design and with character design. Giving the game a huge seamless open world has indeed a big influence on your quest design (while having almost no effect at all on your combat system). You can "fight" against that influence but it needs a HUGE effort and a lot of manhours and money, usually more than what would be needed to offer a really "alive" and "immsersive" open world quest design. As I've said before: both Bethesda and Bioware are no amateurs, they have skilled people and a lot of experience. Both failed hard in delivering a narrative which is even remotely on par with their open world goal. Both failed hard in offering a world design which is even remotely believable or immsersive. All that they could offer was a pretty limited narrative and a lot of filler content on top of that to let their worlds even remotely feel alive. The problem is that I really doubt that these companies did this on purpose. They did a lot of that because the complexity of RPGs and the huge effort of big open worlds don't really go together well. It's basically overambition by definition. The games which offered a believable open world so far were those which we call action adventures (think GTA, Assassins Creed, RDR). Those games don't offer the complexity of RPGs but a quite linear story progression and a quite simple combat and player progression system (and some unconnected side content). Those games in which the open world attempts usually fails are RPGs which want to offer choice and consequence, complex combat and deep character progression at the same time. Call me a pessimist but I just have doubt that some developer is so much better than every other developer that they could deliver a game with the world design and design/production scope of GTA, RDR or Assassin's Creed with the systemic and narrative depth and complexity of a traditional CRPG. That would be THE jack of all trades, indeed the ultimate RPG. I guess we all hope W3 will be that game but I have my doubt. Doubts because I know the business and its constraints and doubts because I see what devs all over the globe were able to release so far and nothing of that is even close to the ambitions of W3...
On the other hand, this is CDPR we're talking about, and this is lore a la Sapkowski and writers like Blacha and Pugacz-Muraszkiewicz. Other Open World attempts that I know of were thin on lore and emphasized Be Anyone as opposed to a personal story. CDPR may actually pull this off. The problem may just end up being not that TW3 will be a failure but that it will be impossible for CDPR to top.