The only reason why it’s easier to climb as a one-trick than a flex player is because it’s easier to get better playing one hero than more than one. If you don’t one-trick a very niche hero (Mei, Bastion, Sym etc), you can roughly climb up to Diamond with any hero. Then it gets harder I would say because some heroes are worse than others and everyone is trying harder.
The SR system doesn’t penalize you for playing different heroes in one game. You can swap at the break with zero impact on your SR gains or losses. Because the stats are averaged out. Say you played 7 minutes with Reaper in the first round and 5 minutes with Pharah in the second round, your stats with Reaper won’t get compared to other Reaper for 12 minutes of play (7+5). But they will be averaged per minute or per 10 minutes and be compared to the averages of Reaper players in the same SR range (and maybe on the same map, etc etc).
The only reason that you can get penalized for switching is if you do it in game and you lose some ult charge. But let say I die using Pharah’s Barrage and I immediately switch to another hero, it won’t impact my stats at all.
If you get little SR for a win, assuming that there are no other reasons involved (average SR of your team way higher than the enemy team, your MMR way higher than your both teams averages, decay, post placements, post new placements, post leaving, etc, there’s a few more) so assuming that everything is normal, then if you gain little SR it must be because you didn’t perform well enough compared to your pairs with the same hero. And the thing is we don’t know what are the stats that the system weigh to determine your performance (to avoid cheating the system), some might not even be displayed at the end game stats page, so it shouldn’t be really something we care about.
The easiest way to climb is not to perform amazingly stats wise and gain 30SR for each victory, but to have a high winrate, meaning to have real impact on those tight games and make your team win them consistently. Usually, performing well and winning more than losing are connected, but not always. You can have good average stats and still have 50% win rate. Good stats and performances don’t guaranty positive winrate. And the opposite is also true, someone can have bad overall stats but because of two decisive plays, make his team win.
Game-changing plays are more important than good overall performances.
Very simple example: two DPS, one has 20 elims but always killed 2 enemies at a time when fights are already lost while the other has 10 elims but kills all his target at the beginning of a fight giving his team a big advantage, which one has better stats and which one is more impactful and will win more games?
How Competitive Skill Rating Works (Season 15)