"V hull" doesn't do anything to protect against mines.

There are three things that can be done: increase standoff, reduce presented area, and increase armor at the bottom hull (belly armor).

The basic, so-called, "v hull" shape of the MRAPs actually looks like:
Hull.jpg

They work because of increased standoff and reduced presented area. The "V" shape is just incidental - it doesn't lead to any "blast deflection."

BTW, these worked well when originally designed by the South Africans because they were fighting LIC in the veldt. Who cares what the silhouette is if you can still be seen coming from 20 klicks out no matter what you're driving? They work well for us today, because we're travelling relatively predictable routes, so who cares if we can be easily seen? In a different type of conflict/mission, different terrain, different threat weapon system mix, etc., they could turn out to be unfixable death traps.

The relevant dimensions for design trades are: presented area vs. vehicle height; standoff vs. vehicle height, ride stability, mobility/agilty; belly armor vs. just about everything.