Season 2 has already announced addressing these issues. The max limit you can queue apart will be 500 when the ranking is bumped up to 5000 max. Current ranking that translates to 10 which seems pretty standard to run into. More importantly if you look at the current player skill distribution +/- 10 from the mean 50, it goes down to 9th percentile and up to 86th percentile. If you translate these numbers to CS:GO's matchmaking (Currently the most seriously taken competitive FPS), the mean is about Gold Nova II/III. You can queue +/- 5 ranks in CS:GO IIRC so that'll let you queue up to ~90th percentile MGE and down to ~12th percentile Silver IV.
Turns out these overlap pretty well, and fair enough for the average person. If you and your friends are as skilled as about half of the game's population (45-55) you'll still be able to queue together. Anything greater than this gap is either a high rank player pulling his team's average down heavily on a smurf to benefit his friend through the underdog system, or people queuing together despite a clear skill difference. Pulled data from
here (OW) and
here (CS) for those interested.
Also that Cloud 9 example in the video was from competitive launch week, which already had issues like KotH maps giving something like 10% of what they should have been giving. Most of the issues involving supports have most likely been stealth patched by now, and a lot of the evidence involving supports getting low rank gain is on personal experience over any actual data. I could say the same thing for the opposite side on how I placed at 49 and climbed to 66 before I started dropping on a daily basis by playing mostly Lucio. I played most of my placements with a 6 stack (which I'm confident in saying I was probably the 2nd best in, next to another friend) and we all placed within 5 ranks of each other.
All the changes they've announce are definitely a step in the right direction for good matchmaking experiences, as the current gap you can queue at is hilariously wide. Someone in the top 5% at 65 can queue with at the lowest a rank 15, which is literally in the bottom 1% of players. You're more likely to see differences of around 20 ranks where skill differences are really noticeable. I'd take the few upset parties not being able to queue together over the unpleasant matchmaking experiences. Division gating for people who reach a certain rank then get really unlucky losing streaks is also really welcomed coming from personal experience.
In regards to carrying teams, it's definitely possible to an extent due to how strong offence characters are at the moment, but working on stuff like aim and communication on any hero will almost always positively increase your performance instead of being a one trick pony. Good communication is the best thing to have against that MLG Genji on the enemy team, as well as adjusting team comps to adapt to the enemy's strengths. (I.E. get hitscan vs Pharah/don't play Junkrat vs her, Winston/Junkrat vs Genji/Tracer, Reinhardt/Zarya shields vs McCree and discord orb that one really annoying guy killing everyone, etc etc...)