Diablo 3 received a ton of criticism during its first year out on the market for a number of reasons. One of the big issues from some of the community was that it was too easy but according to Blizzard the game was actually too hard.
In an article by PC GamesN, Blizzard's Josh Mosqueira talked about the rocky uphill battle Blizzard had to go through with the launch of Diablo 3, first commenting on the game's always-on DRM that hampered accessibility for the game, saying...
“Even our most outlandish estimates for day one, ended up being massively conservative in reality. And it hurt - people had been waiting for ten years to play this game, and the worse fear of an always-online game, is not being able to play. That’s exactly what happened.”... “The sales didn’t matter. The review scores didn’t matter. What mattered most to us was the player sentiment. We had let them down, and let me tell you - that felt shitty.”
There were issues with logging in, issues with the Real-Money Auction House, issues with Linux users and issues with hackers.
Eventually Blizzard managed to get things sorted (for the most part), but Mosqueira had an issue with the game's difficulty, noting...
“The game was so hard,”...“that instead of being these epic heroes, fighting against the forces of darkness, you were a Barbarian smashing pots. That’s right - the best heroes in Sanctuary were farming terra-cotta, because it was more efficient and less difficult than fighting monsters”
This is partially true – the biggest problem was that a lot of people were blazing through the other modes to get to inferno and then getting stuck and then heading to the gold auction house and the RMAH in order to get better gear to beat inferno. The thrill of just going through the game and having fun turned into a grind to get the best gear, sometimes using real money.
A lot of the best items were hard to acquire because the loot drops were tuned around avoiding creating the over-saturation of the auction houses, which in turn would lower the value of the legendaries being sold for gold and real money.
Mosqueira had his own anecdote to share about the game, and his troubles with getting a hold of legendaries, saying...
“When [you] were getting loot, getting bags full of yellows and legendaries, you would know as you clicked on every single one, that you weren’t going to get an upgrade.
Eventually Blizzard closed down the auction houses – both the gold auction house and the Real-Money Action House.
While the PC GamesN article notes that this was done for the best intentions of the gaming community and to help cut down on fraud and middle-men profiting from items sold through gray and black market online web vendors. What ended up happening was that other third-party gold sellers popped up to undercut Blizzard's own auction houses and sell gold and items for a cheaper price, creating a sort of “legitimate” competitive ring of auction houses to stand against Blizzard's own RMAH. It was a mess.
After Blizzard shut down the auction houses things eventually calmed down and they went back to focusing on bringing back the fun in loot grinding. At this stage in the game most people recognize that Diablo 3 is now being built in the proper successor that made Diablo II such a beloved and well-regarded isometric, hack-and-slash ARPG.