I've been on the 320 fam quite some time now and this is the first time I've heard of this 400' thing. I my experience, GS Mini works perfectly as advertised and those who bad-mouth it either won't or can't try to understand what it is doing for them.
But the key is to have an accurate Tower wind in the box. Quite a few folk put the Atis/Volmet wind in the mcdu and wonder why strange things happen (perhaps as described above) when actually the tower wind has changed markedly since they entered it. So why not update the wind when checking in with the tower or when the guy in front receives an update as he is cleared to land.
Cheers
mcdhu