Maybe it is just a coincidence, but as soon as I got my star it has been taking several minutes for me to find a match.
Two of the biggest positives for this game compared to League of Legends, for me, have been low queue times and short games. If queue times go up to 5+ minutes like League was for me (even in low silver), then I may stop playing this until competitive to see if it boosts then.
I'm only level 50-something so maybe I'm okay for now.
About character stacking, almost every time I see more than one of a character, it's frustrating and not very fun or rewarding. I beat a team who had 2 Reapers. Pain in the ass. Used a balanced team to beat 6 Meis on payload. Pain in the ass. Played against 2 Genjis (not sure if we won). Pain in the ass. *edit* 2 Pharahs chaining ults and taking out snipers to prevent you from stopping ults. Pain in the ass.
One of the only fun stack games I've been in recently was when we tried to troll with 4-6 Meis, only to realize the other team had trolled with 6 Pharahs. We immediately switched to 4 D.Va + Mercy + Symmetra. They never even got the first point, though they started mixing characters a little in the last minute.