I think the team behind DS2 genuinely believed that unforgiving difficulty was what made a Souls game. They really messed up the combat with insane tracking and hordes of enemies (which I hear was made even worse in SOTFS). And then you discover aside from the first few areas that the level design is a shadow of the previous game. It just never felt like a proper Souls experience. It's still a very good game but I can't even properly articulate how disappointing a lot of the game was.
As long as DS3 goes down a similar route of Bloodborne (which I'm sure it will with Miyazaki's team working on it) it will be perfectly fine. The game's difficulty will tie in beautifully with the level design and bonfire placement. The game will feel challenging but never unfair. The combat scenarios will be interesting & diverse whether it be fighting your run of the mill enemy or a boss.
Many people claim that the DSII dev team did not understand what make the souls games great but I think this is BS to be honest. DSII team and the Bloodborne team came up with different solutions to some problems both Demon's and DS had when it comes to the actual combat mechanics. There's a reason why both DSII and BB are different to them predecessors: the combat in DS is trivial when you learn that you can parry almost anything and you can backstab almost every enemy in the game; both things were not intended at all so they had to make adjustments to the combat mechanics to prevent that people already familiar with the previous games abused those resources, and that just tells you that they wanted to improve the souls formula, not just make things harder for the sake of it.
These are some examples of what they tried to change:
-Execution of parries in DS2 had a very different timing than in previous games; in BB they tied parries to the use of a consumable item to prevent people from relying too much on them. Before the first patch, players would have to farm quicksilver bullets if they relied too much on guns or if they failed frequently while trying to learn this new parry.
-backstabs in both Bloodborne and DSII work different than in previous games: in Bloodborne a backstab require 2 steps, charging your attack and then punishing the enemy; in DSII backstabs are trickier to perform and the enemies can hear you easily so performing one is kind of risky. BB's solution to this issue is actually better because it prevents the player from circle around the enemy to fish for a backstab, something than can be done quite easily in Demon's and DS. In the other hand, to prevent the player from doing the same in DSII they came up with a less elegant solution: now the enemies can track you and they can hit you even if you're right behind them.
-another thing BB and DSII did to be different to the previous games was the presence of mobs. There are much more mobs in DSII and Bloodborne than in demon's and DS, and those games demand the player to know how to deal with them, but at the same time they provide the player with different resources to deal with them. In BB you're faster, your actions cost less stamina and even if you got hit by enemies you have the regain system that allows you to regain health while attacking; in DS2 you have access to a ton of recover items like the gems, and if you spend some experience to level up adaptability you can use those items faster in the middle of the combat and your roll does have more iframes too, also using two weapons can give you access to a whole new set of movements that would give you some advantage to deal with mobs.
-they also tried to improve the way you play online by adding stuff like soul memory or summoning and invading by using bells. Of course, when it comes to the online component of those games, you can make a whole new discussion regarding wether or not those systems worked.
Anyways. I want to know what Fromsoft do to tackle some of the issues I mentioned. We already know that parries are now restricted to the use of a certain type of shield, so it's pretty obvious that they are trying new things to try to keep the games from being too familiar to experienced players.