It will raise her inner sight and cold/fire arrow by one extra level, not that it would make a big difference at all.

No clue.. but I heard with the changed ias breakpoints in d2r something fancy can be done with diamond bow

You can reach 6fpa now.

For PvM damage wise is lower than 7fpa with atma, razortail and forty, so it's not worthy.

PvP I can't, but looks like can be huge.

not sure why ppl are referring to D2R. The D2r discussion forum is here: https://forums.d2jsp.org/forum.php?f=148
for D2, i see no reason to use a Faith Matri to PvM.
for PvM, using faith, I would always use a GMB.
for PvP there are several options each with their own merits in certain situations (GMB, Diamond, Shadow, Matri)

is this a multishot build or strafe

Multi is you main attack, is so much more damage than strafe, you still use strafe since it can be better in some scenarios.