If you're not gonna add soloQ.....

You need to greatly restrict the limitations. Right now and even in previous seasons, it's been far too lax.

If you've played about 200+ ranked games, and you've at least started to settle in where you belong, you've likely noticed ranks deviate very little. You'll likely play with players in 1-3 tiers of you max. You won't encounter players in entirely different divisions in except when you're at rank 1 or 5. However there will be stupid little games when you're up against a player who is in another division entirely, and there's no obvious explanation.... well it's because they're in a premade group effectively ruining the matchmaking as a whole.

So if you wanna play with a random amount of players, by all means, but there needs to be a much safer limit. Say 4 divisions or 1 tier max, whichever comes first. So a G1 could only play with a G5, Bronze 3 with silver 4 etc....