A melee Necromancy/Warfare build was found to be too OP in beta. Necromancy was healing twice as much as it is currently in game. That was made the build OP. The build is still great. I have been watch a D:OS2 play through and one of the two people have Fane as a companion and have been playing him Strength build sword and shield, going mostly Necromancy and Warfare. It works well with an undead. As you mention, two points into Geomancy is great for Fortify and Mend Metal. If you have enough points in Necromancy, you won't need poison to self heal. However, since you will have the two points invested, you might as well grab them just to be able to do some magic damage.
If you want to go Intelegence build with the character, things do get a bit tricky. Don't rely on a poison staff as you will face many undead in the game and it will heal them. Going with a build like that will be a bit tricky. Warfare will augment the damage you do, but you will still be doing magic damage while using a staff in melee. That means you will need to rely on others to strip physical armor off of opponents so Battle Stomp and Battering Ram will be useful. I don't want to discourage you from doing this, I am just warning you that a bit more party coordination will be needed. However, if you put that little bit of extra planning in, speaking from experience, it does work well in a split damage party.
I salute your out of the box thinking and wish you well on your new play through.
