I agree with you with Dragon Age II failing to create an atmosphere, along with failing to do almost everything else. There's a lot of reasons why I disliked that game, some are just nitpicks some are bigger reasons. I hated some of the new characters and what they did to some of the old characters, for example, Flemeth who showed up looking like she just walked out of a JRPG. Then there was Fenris, don't even get me started on him... I only liked two of the characters, which were Varric and Merrill, even Anders wasn't as good as he was in Awakening.
The combat was awful with Hawke swinging around his sword like there was no tomorrow with moves you would expect to see in JRPG and the gore, the gore I felt was handled very immaturely. In Dragon Age: Origins when you would get in a fight blood would spray on you, there wasn't too much there wasn't too little, it was well handled. In Dragon Age II all of that was thrown out the window and while blood still sprayed on Hawke (only on the front this time which made more sense) enemies would also explode into a puddle of blood if hit with a powerful attack at low HP and it just looked fucking stupid. There was also no reason for tactics in the combat with so many waves of enemies rushing in, there was no real point, it just quickly became the case of just charge in and hit things.
There's also the complaints about it being rushed and how it was a 30 hour long game of 7 copy-pasted rooms, even the part of the world you explored wasn't very big. One city and some area's around the city. I loved Dragon Age: Origins, I've completed it about 6 times and it's one of my favourite RPG's this gen. But I couldn't even do a 2nd play through of Dragon Age II. I bought Dragon Age II expecting more of Origins and I got a rushed out steaming pile of game.