Why are rings unique equipped?

[ElHeggunte]

I play DRG, I am currently using the 180 ring of Slaying and Fending. The fending ring has Determination and skill speed, 2 stats that DRGs can use. Each ring has a stat that all classes use.

I see people do this a lot and I've always wondered if the secondaries on the "off" ring outweigh losing so much of your primary stat.