AbdulAlhazred
Legend
This is really the main point for me. All strikers are not the same, and even different builds of the same striker do not need to be the same in defenses, accuracy or damage potential.
One reason I see for Rogues getting a boost is that they will only get the OAs if they are in melee (unless I miss something, it is nearly impossible to get and OA with a ranged weapon) so that is a major drawback for the rogue right there. A ranger shooting form 20+ squares away is nigh invincible.
I think Twin Strike with a greatbow by itself is explanation enough. There are plenty of ways for a tactical situation to evolve where monsters can get into melee range with a bow ranger and I wouldn't call them invincible by any means. They are however not in need of further damage boosts.