The June 13 patch made Tier1 Gunpups better at aiming, their Undead cousins were not so lucky.

Also I'm not sure if this is a bug or intended as a side effect of tier balance but by standing in the right position in front of a Tier 2 rocket before it's homing kicks in can cause it to decide that a collision course with you is a bad idea and instead viering off to the side and missing is a better idea.