There's such a thing as moderation you know??
So how's the coop
It works very well! I have no trouble finding people to summon me for several bosses, players seem generally less idiotic than they are when just exploring a level...
As an Heir of the Sun, you frequently find yourself summoned along with someone else. This makes the actual fights pretty easy if you know what you're doing. Enemy HP and sometimes quantity scales, but their damage does not, so you can cordon off the game's frequent multi-enemy bosses into areas of responsibility. Or just surround a giant slug and beat the poor thing to death.