[1.2.304] Strange items...

There is no reason to suspect that Stun Mastery is intended to add 300% damage with SE.

There's no reason to suspect that sharp eyes is intended to add 140% damage either. The fact that it happened in two versions simultaneously is reason enough to expect it to be permanent and intended.

Similarly there is no reason to suspect that self SE is intended to add 125%

Except neither of us know that it adds 125% damage.