The missiles can collide with, say, a pillar in the goblin-occupied temple to Selune
I believe that is what they dont like ...
They want (if i understand this corectly) that one dart that would colide with pillar to fly other way and hit the target as the other two did.
I dunno ... i gues need to create free space between caster and target is simply cost for absence of hit diceroll ...
And honestly i kinda liked how it works now, and didnt had even single problem with it. O_o
I admit that i dont know DnD rules so well to argue if you are or are not suppose to do this or that ... but i would presume that in this case rules arent exact enough to work alone, and GM is required ... personaly i would probably not allow my Wizard to kill (if he does enough damage) anyone with magic missiles if he see his leg, or arm while he is hiding behind a pillar ... but i gues its up to people. :-/