Surely the biggest flaw is that combat remains clunky. Sluggish controls and awkward camera angles mean that you can never really get into a smooth flow of strike and counter strike. This is a story based RPG and not an action combat game so you could insist that fluid combat is not actually required to enjoy it and you would be right. However as well as being a terrific RPG Witcher 3 is also almost a terrific open world action game than could compete with Assassins Creed, Shadow of Mordor or even Far Cry 3/4 if not for the clunky combat. Given a choice I think the developers were right to prioritise RPG mechanics and story over fluid combat but just imagine if they had pulled off both?
My only major niggle is the uneven levelling curve. It seemed to take me forever to get to level 5 and during those early stages I was exploring a dangerous world where most of the monsters and quests were above my level. From levels 5 to 10 things seemed to speed up and 10 to 20 went even faster still. The world around me did not keep up with my levelling. My quest book soon became full of quests I had out levelled and the game as a whole became much easier. Plenty of others have made similar observations on forums and in reviews so this isn't just me. Somewhere in the mid teens I made a concious decision to concentrate on the main storyline and ignore side quests in order to slow down my levelling and maintain some challenge. This approach more or less worked and I was fairly on level when I finally finished the game at level 32/33 BUT I had to leave out a lot of content along the way.
Lets us talk for a minute about the side quests. First off there are an awful lot of them and most of them are really great. The quest log has Main Quests. Witcher Contracts and Treasure Hunts. Those actually called "Side Quests" are multi stage mini-adventures with engaging storylines that sometimes overlap the main quest and can even influence the eventual outcome of the game. Witcher contracts are picked up from a noticeboard or a villager and generally involved killing a named monster for a reward. Treasure hunts often lead to high quality gear but they can be multi stage and may ire you kill monsters and clear out dungeons to find treasure. In addition to these explicit quests the world is full of villages that have been over run by monsters. Clearing out one of these abandoned villages will net you some XP after the villagers have returned and will often provide a new vendor and a new fast travel point. In addition to all of these quests there are also rich equipment crafting and potion brewing activities both of which require searching for ingredients and recipes. Then there is a fully fledged collectible card game embedded in Witcher 3 that you can play with characters all over the world. This incredible bounty of things to do is what makes Witcher 3 magnificent but the fact that they all seem to give experience which levels you up is a problem. If you skip most of the sidequests as I did to try to stay on level for the main quest you miss so much of the game.
This is a known problem in any level based RPG that tries to have an open world full of side quests? I remember Oblivion had the same issue and tried to solve it by levelling up monsters as you levelled up but that came in for a lot of criticism from disgruntled players who found them selves facing beggars in jewel encrusted armour by the end of the game. If all the enemies level up as you do what is the point in levelling up? I have a different suggestion that I think would work better for Witcher 4 if that every becomes a thing. I think that there should be a level cap and I think that most of the games content should take place at the level cap. Progression need not stop entirely at the level cap. You can still upgrade equipment and perhaps discover new skills. Progression beyond the level cap should increase the variety of options available to you rather than just give raw increases in power. I think this would work very nicely with the free roam mode than is unlocked after you finished the main campaign.
Finally a word about endings. It has always been a feature of Witcher games that your actions have consequences, sometimes unforeseen ones. Your decisions during a seemingly unconnected side quest can influence the fate of the characters involved and may even have wider implications on the overall outcome of the game. Many of the key decisions are heavily signalled with a timer bar which counts down while you quickly choose between a number of responses. This does seem a bit artificial but for the most part I went with my gut response and stuck with it. In several cases the outcome was not what I would have chosen but the quality of the writing is such that even in those cases I had to agree that the actual outcome was more fitting given the circumstances that what I might have preferred. I don't want to give spoilers but I will highlight Geralt's love life as one area where the outcome definitely wasn't what I intended but actually made far more sense. I will admit too that I did cheat at the very end of the game, After finishing for the first time and not getting the outcome I desired I realised that one of the side quests I had ignored was essential to achieving my desired ending. Happily it wan't too far back so I loaded an old save game and replayed about three hours worth to finish the game the way I wanted to.