That is a bit reminiscent. One the other hand, all of the major Avengers have had dying scenes. On the other other hand, none of the others have had one in Avengers. One the hand from before, having the team actually kill him and he stay dead is new ground. One the other? hand, Stark really does have to be there for A3, and he's kinda difficult to bring back.
So... maybe not Stark, I'd still keep the team-has-to-beat-him-within-an-inch-of-his-life thing, but the death part just doesn't have the same punch.
Now, Cap, he actually needs to die in order to set up for Fallen Son/Rebirth of Cap in Cap 3 to bring the Time Gem thing to Thanos. It could be done near the onset of Cap 3, but as a clincher or denouement for Avengers 2 it works, especially if Ultron is specifically taking out the Avengers, cutting off their leader to weaken them so that they cannot rally. It makes Ultron look smart and Cap look important, when they cannot function without his leadership, so when he returns to form in Avengers 3 it's like "ASSEMBLE!!!!!"
And then you kill Thor too.