I played OW1 for years and was staying at around 2700 plat player all those years.
Then in OW2 I played QP for a a long while and just went to ranked and calibrated at… bronze3? WTF? like maybe I’m slightly rusty but not bronze tier rusty. 
nah i got bronze3 and im much higher myself
the trick is to look at your promotions, if you are going up 3 ranks each time, for instance youre bronze 3 and you get a promo and hit silver5, then your mmr is much higher than your actual bronze/silver rank, since it will continually skip you up 3 per promotion to try and speed up your visual rank to your actual mmr.
for me each promotion was 3, so i went from bronze 3 to silver 5 to silver 2 to gold 4 to gold 1 to plat 3, etc. once you stop getting the sets of 3 on a promotion then you are now approaching your actual mmr.
the visual gold/silver/bronze/diamond thing isnt actually your real rank its just a “visual grind”
Well if you’re 2700 and you got bronze then you should be able to carry games and climb out pretty easily.
You won’t be bronze 3. I doubt you’ll be playing with bronze players. You’re labelled as bronze so you can “climb” throughout the season and feel a sense of progression. Your rank literally means nothing anymore.
This, if you play just two sets of games to get a rank update, you’ll find your rank up 2-3 tiers a time. Then you’ll start to plateau a bit more as your MMR approaches your actual rank.
yeah seems like Blizzard did one of their stupid design features again where they take a competitive mechanic and make it casual
This is by design. You will need to grind up through elo hell. I just hit Diamond 5 and I’m just beginning to be be matched with players more consistently that understand the game.