Fire KFM - Ring Progression

I haven't gotten the BT fire ring yet, so I was curious the progression of DPS and what it should look like for gear in regards to the ring.

I have heard the elemental ring is not as good as the earring, but why is that?

With that mentality, does this progression make sense?

Pyro Ring ---> True Yeti Ring ---> Destiny Ring ---> Ignitor Ring.

I have yeti ring right now. Is it worth getting Destiny or should I wait for Ignitor?