Well, as Budos said, generally faith doesn't worry about str/dex at all. Only enough to barely equip the weapons you want/need. 16 is a good mark for str since it lets you use the claymore, and you can 2-hand the zweihander for specific bosses.
on the dex front, most people want at least 12 to use the bow, but 14 lets you use the great scythe or uchigatana
20/16 gets you the washing pole, which is kind of like the halbred of katanas.
My personal favorite weapon, the lucerne requires 15/12
You "can" use the grant if you want to build specifically for it, but I wouldn't recommend it, throwing lightning bolts is more fun, and dex/faith is a much stronger hybrid build than heavy str+faith.
40 vit
30 end
14 str
40 dex
50 fth
You can use occult/divine dex weapons.... or also just go +15 and use the darkmoon blade buff for "massive damage" and with that build you'd have the dex speed casting bonus. Generally dex weapons swing faster, so you'll do better off in lighter gear, but 40 end isn't the worst thing in the world either.