My blackguards don't usually wear these but...

[sffp]

c) a Ring of the Mouse (+0,-3) <+4, +2>
Found lying on the floor at 1250 feet (level 25)

+4 dexterity.
+2 stealth.

This is actually improving my Tulwar of Frost (2d4) (+5,+8) more than the Reckless Attacks was.

[Ingwe Ingweron]

c) a Ring of the Mouse (+0,-3) <+4, +2>
Found lying on the floor at 1250 feet (level 25)

+4 dexterity.
+2 stealth.

This is actually improving my Tulwar of Frost (2d4) (+5,+8) more than the Reckless Attacks was.

That's the lowest malus on "damage" that I've ever seen on a Mouse ring. The +4 Dex, with the extra blows you will get with your weapon, will outweigh the ring's damage penalty for a very long time. By the time your @ Dex is so high that the ring won't help, you will have long before ditched the ring for something better.