Are Bards strong enough/sturdy enough to solo in melee combat?

[Naethyn]

Warriors get something like 0.45 rAC per worn (visible) AC. That means for every 10 item AC they get 4.5 in the ATK vs AC calculation. Bard is down with casters at around 0.24 rAC per worn AC. Even though they wear plate they mitigate far less than say a ranger, or rogue in chain armor.