I also think the gun isn`t really well implemented in the combat of DSII. Other then that it`s good. I think Bayonatta did the Gun-combat in conjunction with melee-weapons best.I bought and played Darksiders 2 today. The combat mechanics are freaking awesome, along with the added loot and puzzles you have to solve to get to where you're going.
I only played up to where you get the gun. It was at that point I lost quite a bit of respect for the game. Why bring a gun into a game about hacking and slashing and performing awesome combos? It ruins so much for me...
Ever heard of a little game called Devil May Cry?
Also they had a gun in the first Darksiders. It could be anything, it's just meant to add a different strategy to your combat with ranged attacks.
I played a bit of Darksiders II and NSMB2 today but haven`t accomplished a specific goal with them.