Well I wish you could see what league you're placed in all the time when playing ranked. You have no idea if you are playing with people in the same league as you.
Agreed, especially since even on diamond III I feel like sometimes my teammates are on their first game, judging by the way they're playing. Not their fault if so, but I'm not convinced that matchmaking is working as intended. But maybe there's not enough players in the higher ranks to fill up the matches, so they get replaced by players from lower ones? Hopefully this will resolve over time.