The problem is too many characters were killed off in ways that felt very abrupt and unceremonious. Their deaths didn't have an impact because they had no real build up, too many were killed because of shock value or story convenience. These kind of deaths don't feel dramatic, they feel cheap and meaningless.
Daredevil died off panel, that's a real waste, he didn't even get to have an awesome death scene, instead he dies and we never see how. Comics is a visual medium, show don't tell. Heck pretty well everyone who died in Ultimatium got a death that was cheap and meaningless and in the case of Wasp down right disrespectful.
Its not just Ultimatium that wasted characters in rather meaningless deaths. Look at the way Sebastian Shaw died in UXM, he dies 3 or 4 issues after his first appearance and he just gets melted by the Phoenix. I think they could have down more with that character, I don't think Sebastian Shaw is a fundamentally lame character, look at how Shaw was handled in X-Men First Class, he was a great villain there, better then in the comics. First Class Shaw seems more like a better alternate version of Shaw then one in UXM. When Sebastian Shaw died in the movie, it was powerful moment, it symbolized Magneto getting revenge and trying his back of Xavier's ideals at the same time. When Shaw died in the UU, it was meaningless.
That's the problem with killing off characters, when they die you cut off a potential avenue for telling more stories. There still could have been more stories to be told with Wasp, Daredevil, Angel, Cyclops, Wolverine, Shaw and frankly anyone who had a cheap death. I at least liked Spidey's death, because it had a build up and didn't feel cheap and meaningless.
UU writers should either have a moratorium on killing characters or should only kill characters when they can figure out how do it the right way, having a awesome or meaningful death scene. UU kinda shot itself in the foot with all these shock deaths.