Honestly, I think having this indicator will help a lot more than Riot expects. They can quote statistics all they want, but people are always more swayed by specific anecdotes and personal experience than numbers. Being able to actually see "Oh, those two had good synergy but they weren't actually in a group" will eliminate false positives of losing because the opposing team had a premade group and yours didn't, and it will also allow at least some counterplay like "I'm the top laner on my team with a duo bot lane, the enemy is duo top/jungle. I should play safe in my lane to survive ganks and try to use teleport to snowball our ADC." It might even alleviate some of the frequently voiced concerns about how much of an advantage a large premade has, since it would be easier to notice just how often a 4-5 man group matches up against the same distribution, nullifying the advantage.
That said, I think Dynamic Queue makes more sense for Normal games. Having a single ranking doesn't properly demonstrate the substantial difference in skills used between fully solo queue and full team queue. I say if you're looking to have fun with friends and can't get a full 5 together then normals should be plenty for you.
And if they're dead set on Dynamic Queue (as they've pretty much stated they are) then (GOOD) in-game voice chat is a requirement. Even if their algorithms somehow become perfect and there are no occurrences of games with uneven premade groups, the role popularities even out so queue times are reasonable for non-support players, and the semi-legitimized Elo boosting from smurfs making a premade with legitimate low Elo players gets fixed... You still end up with the problem that a solo player matched with premades has a worse experience than a full solo experience. Voice chat will improve that quite a lot, and also compensate for some of the imperfections.
