You'll definitely need some vit if you cannot have very good gear. Dexterity is also a must have, you need approx. 4 times your lvl into dex to almost never miss. Anything in between works, since you also get an accuracy buff, and you can use 10% accuracy socket stones from Sundries NPC on both main- and offhand weapon.
So, basically 2str 1d 1v.

However, if you can plus your weapons (eventually to +10) every now and then, you could probably go 3vit 1dex and forgo on strength altogether. Nobody stops you from restatting at endgame, anyway.

As for skillbuild.. I'll leave that to someone else, as i'm a defender myself.