The slowing down over an enemy and the bias towards horizontal and vertical movement - these are things that all "good" console shooter control systems have in some degree, to compensate for inherent limitations of console controllers. If it's done right, you shouldn't notice it, but obviously it's possible to overcook it, making the controls feel stiff. But similarly, you would notice it if it wasn't there - Deus Ex: HR, for example, features no slow-down when you move your reticule over an enemy, and the shooting feels a bit clunky and imprecise as a result (on consoles - this doesn't apply to mouse or pointer controls).
The rate at which the view responds when you move the stick is often handled with a curve... the first 60% or so of the stick range actually represents a relatively small movement of the screen, after which it rapidly accelerates. If this feels off, it's probably one of two things - either the curve isn't right, or there is input lag. It's really important not to make the curve rise too quickly at the start - you should be able to make tiny tiny movements of the reticule, so that it barely moves at all... if the screen moves too fast too soon, you'll find it very difficult to aim precisely. But it's also possible to make the curve too shallow - in this case you experience the view moving very slowly for a long time, then suddenly speeding up all in one chunk, probably overshooting the target...
As to why the dev team might not spot a potential problem - if you play the same game all day for weeks and weeks, it's possible to become habituated to anything! Only user testing would tell you if there's something wrong, and probably you would need hardcore players who could articulate exactly where the problem lay. One possibility is that the testing of U3 was skewed towards more casual players, who might feel that something was off but not know why, or attributed any aiming troubles to their own lack of ability - such players might not flag the issue in sufficient numbers to get the attention of the devs.