If all weapons have stats like puncture, slash, crush, reach, weight, durability, block/absorb, parry/trap, deflect/avoid, speed etc etc etc, it doesn't really matter if it's one or two handed. It should mostly governs fighting style and what perks we get access to. A heavy two handed claymore might have very good blocking abilities, maybe not as good as a tower shield, but enough to absorb much of the incoming energy from a heavy war axe. But you might be weak against an agile opponent, whereas being a dagger user yourself you get to be agile enough to avoid blows but won't deal the same amount of damage. You should feel quite powerful with the path you choose to take, but there should also be situations where you go "damn, I wish I'd taken something different". Every weapon should have it's strengths AND weaknesses - no ultimate winner.
Like in FONV, the weight of .50MG ammo and speed of the anti material rifle makes it an awesome weapon to have around, but basing your existence on it alone may prove difficulty. Carrying a secondary and even third weapon helps on being more flexible in battle, but has a significant cost on weight. It's all about having to make a decision. If your two handed claymore or great sword proves difficult against agile opponents, just bring a dagger or magic, and pray you spent important perks there as well instead of useless abilities like double running speeds - which might *also* be a valid tactic to get away
I don't think any weapon (incl. magic) should be the ultimate solution to all situations. They should make us want to specialize to get better with our weapon, but also make us want to generalize so we have a better chance in some situations. Forcing the player to *think*, and *choose*, always makes the best gameplays. Especially in RPGs.