If you want a good reaver build, why not just go Weapon and Shield? You do not need to spend points in the opposite tree just to get a few extra survivability points. Plus, a shield adds more protection and other effects that can be very helpful to a reaver.
Well basically, since you don't use any abilities for damage besides dragon rage, you can definitely choose between W+S and 2H. However, just because all the passives are in the "opposite" tree doesn't matter for 2 handers. It's not like you'll actually use payback strike or lunge and slash as a W+S reaver (these are the two actives required for turn the blade and turn the bolt).
Even shield wall you should never be using as you shouldn't be tanking. If you do decide to tank/offtank I think you'd still be better served by using combat roll to evade any strong attacks, and any weaker attacks you you can shrug off with your passives+crafted armor.
So to sum up the pros of each weaopn type for a DPS focused reaver:
Weapon + Shield:
-Shield increases survivability (more armor, more ranged defense, etc.)
2 Handed Weapon:
-Higher base damage (dragon rage hits harder)
-Can use the Reaver focus ability (although this will probably be patched)
So really the difference between the two is negligible. The main thing is that none of the weapon-specific actives from each tree are particularly useful for a DPS Reaver, so weapon choice really doesn't affect playstyle at all, just whether you lean more towards survivability or damage.
That said it does seem weird that as a 2 handed weapon user you are speccing into the W+S tree, so if you are against that from a role-playing standpoint, by all means go W+S.