Matchmaking; something is wrong with it, just take a look at various topics on it.
Here's a few ridiculously simple solutions:
1. Do not give premade teams such a HUGE (might I add GROTESQUELY HUGE) supposed advantage for simply being a premade (do not raise their ELO rating so drastically as a team). I would imagine that a lot of premades are low level people playing with their friends not ELITE level 30's all playing together.
2. Only allow people to be matched with somewhat equally levelled people (e.g. if your team has four level 8 people and a level 30 person, the opposing team should have four level 5-10, and one person level 25-30). Pretty much place level bracket restrictions when making a game
3. Do not worry too much about que times, I 100% guarantee you Riot that EVERYONE would rather wait 5 minutes and have a fair fight, than wait 40 seconds and go against all level 25+ people
Someone at Riot please do read the following: I told a friend of mine to play this game, he does now, he's level 7 at the moment, and he's considering buying IP/XP boosts (so he is pretty much a paying customer). He likes playing the game by himself, games like these are 100x more enjoyable when playing with friends though. Here's the shocker though: he DESPISES playing with me and our other friend who plays this game (I'm level 23, the other is level 14). You know why he hates playing with us? Because he usually rocks games that he plays solo, when we group up, he's a level 7 while we get matched up with very high level people (I'm not joking, one game we were up against THREE level 30's). The MM system literally does not allow friends to play together. That's the main point.
TL;DR: make level brackets for MM, for the love of all that is good stop giving such an insanely huge supposed advantage for queing up as a group/premade/with friends.