Thats why its always solo/duo and 5vs5 in every normal game with ranked mode, unless the community that game have is huge (like overwatch, where there is dynamic que but it almost always put 3/4/5 man premades with other premades).
At high golds and above its pretty much impossible to balance premades against solo players, there isnt enough players around (and even if there were you will reach a point where its impossible).
When we first time had ranked premades vs randoms didnt work out, why does SD think it will work this time ? You shouldnt be forced to form a team just to compete at higher ranks, thats fucking insane, if i wanted to do that i would in a proper team while taking part in normal cups and not farm randoms in ranked. As soon as people farm out those aura cards/trinket ranked will be as dead as it was first time around, i guess people that run full premades will be happy playing against the same 4 premades constantly.