I've played the whole game two-handing the biggest, slowest swords I can find with no shield. If anything it's too powerful a playstyle. Like any other weapon, you just have to pick when to dodge and when to attack. I really feel like every weapon I've come across (and there are so many!!!) would be viable with the right investments, just like in Dark Souls 1. It's just a matter of how you like to play.