The 1-in-flight rule would not help all of the current wasted procs that I am talking about. The problem is DoT ticks overlapping each other and on occasion constantly re triggering Shooting Star's in a 0.2-.04 second area, you simply just don't have time to use your first proc within that window, if you are on GCD from any other spell.
Frankly that only happens a very small percentage of the time and probably not worth fixing, the bigger issue for me is when I am casting the loooooong nuke (like the one where I can get up, get a cup of coffee, watch some TV, take a nap and then come back as it's finishing casting) that we call "Starfire" aka "SlowFire". That 2+ second cast is a great time for back-to-back SS procs that overwrite each other.
I notice it the most with any major cd's popped, CA ( obviously, both dots have no GCD time between ticks), and hero. So anything that gives us more haste or makes our dots closer together. That's why I am worried about more gear, where we will get more DoT ticks. That and long Starfire casts are never helpful. I see only benefits to my suggested change, which I realize can't be the basis on which Blizzard gives any class anything.