Yeah, i think the key here, as others have mentioned, is that Normal and Savage are different contents that need to be in their own groupings. A Normal 8-Man A1-12 should be effective... i mean, when i have gone in there using duty finder it is as clean and quick as is usually with the trial roulette.
And for the 24 man content, there's sometimes the adventurous run, sure, as with trial roulette, but mostly other than the newest content, it tends to be pretty clean. Once Stormblood is out, there will be 6 of these contents, so a Roulette for those should make a lot of sense by now. The 3rd tier in each set of 3 would always be a bit tougher than the other 2 but completion rates and time will still be good.
At least getting these two going would be a start. Coil and AS are a different beast though ... hopefully more solutions can be found to keeping that content at least somewhat active as the quality of it is generally fantastic.