Here's something about Dead Shot that makes it quite nice for crit-fishing. If any of the attacks in the Dead Shot crit, the whole thing crits if you confirm, so improved crit would be a significant damage increase at high levels. At 11th, having improved crit changes your crit threat chance from 1-(19/20)^3 = 14.2625% to 1-(9/10)^3 = 27.1%, so it's like you're crit range increases with your BAB (34.39% with improved crit, 18.549375% without at 16th). All of a sudden you're effectively wielding a 14-20 / x4 weapon. This gets juicier if you allow haste etc. to give you extra attacks in your Dead Shot.