You're basically asking the raiding playerbase to have to consider not just 2, but 3 rings now when planning what to upgrade for their job(s). Based on the job, it would go like:

"The left ring has Skill Speed but the right ring has Crit, but the Savage ring has even more Skill speed but I might get get it this week. maybe I get the tome right ring and upgrade it to max and pray that the Savage ring drops...oh wait I completely forgot about crafted rings....fml"

Yeah this seems like a bigger headache than having 2 perfectly matching tome rings.