Let's take me, for an example.
If you look at my Pre-Rework Shen and my Braum, you see over 3.5 KDA and over 60% Win Rates on both Champions for my Ranked Career.
On Pre-Rework Shen and Braum, I'm likely a Gold Level Player.
However, I didn't want to get to Gold and only have 2 Viable Champions. Instead, I wanted to raise when I was ready to play Multiple Champions in Multiple Roles. Of course, now they come out with Dynamic Q where I'm highly likely to get my best Role... so this division isn't needed now. But the point was, I wanted to be a Gold+ PLAYER, not a Gold Plus Champion or Two.
So I've played almost every Champion in Ranked since Pre-Season 4 when I started. Not all of them, but probably 90%+ in actual Ranked Games. It's because I want a Roster of Champions to take up with me, and for me 2.5 KDA and 60% are the Stats (metrics, if you will) I use to justify a Champion 'worthy' of rising (minimum of 10 Games).
So had I just only played Braum and Pre-Rework Shen, I'd likely have already climbed... just to get to Gold or Better without a full skill set and very limited Champion Knowledge, likely just to be brought back down when forced to play other Champions.
Also, I'd like to take a moment to address 'Elo Hell'.
Elo Hell does exist... but it's not what people think. You having 'dumb' team mates is NOT Elo Hell.
I placed myself, unintentionally, in Elo Hell at Season 4. I had horrid Placements, largely due to the fact that (1) I sucked, (2) I had no Tier 3 Runes and (3) I had exactly 16 Champions. In other words, I went RIGHT to Ranked, and it was WAY to early.
So my MMR starts to drop, as it should. Not complaining here at all. That is as it SHOULD be.
But then I started to notice an awful lot of DC, AFK and Troll. So I was running into Bad Internet Connections (DC), flamers quitting (AFK) and Trolls feeding free Wins to the Enemy.
I was so bad, I had dropped my MMR to the level of guys who either can not Win because of Internet Connections, can not Win because they get pissed and Quit, or can not Win because they CHOOSE not to Win. Imagine how low that MMR must be.
THAT is Elo Hell. The point where your MMR is equal to those who have hamsters in toasters for a PC, your MMR is equal to those who have Tourette's Syndrom because the Support hit a Minion with a Basic Attack, your MMR is equal to those that INTENTIONALLY LOSE.
Once you are in Elo Hell, it's all 'chance' at that point. Because there WILL be an AFK, there WILL be a DC, there WILL be a Troll. Now STATISTICS will say that the Enemy Team will face this as much as you will... but that's a general and inaccurate statement.
I faced an insanely high Rate of Disrupted Games of 52% in Season 4. That means in 52% of the Ranked Games I played, there was an AFK or DC (I didn't even count Trolls). Of those, 82% of the time it turned out MY Team was at the Disadvantage.
Somewhere in the world some lucky bastard was only having an AFK/DC on his team 20% of the time, and some one else was 50/50 to even it all out.
I got the statistical short end of the stick.
Which meant as I improved as a player, it was still very difficult for me to carry when at the Disadvantage so often.
THAT is Elo Hell. But the caveat is that YOU put YOURSELF there for it to happen. And that there IS a chance that it affects you far less than others (you might be the lucky guy only having the disadvantage 20% of the time, meaning 80% of the time you play AT an Advantage, helping you get out even quicker).
Since then I've climbed to BI, then pulled back trying riskier Champions in more 'Carry' Roles. It wasn't until just this Season that my ADC Game is nearing the point I'm ready to move on with it, and my Support and Engage Tank are already there... so just things like Assassins and Mages really left and I try to start a legit climb with a full pool of Champions.
But I'd put my Braum, my Pre-Rework Shen up against anybody up to and including Gold Level Players (and have, in Custom Games). I'm starting to get to Silver/Gold Levels on more Champions as well. And thanks to playing a ton of Support and a ton of Shen, Map Awareness and Warding are skills I pride myself on. But I'm not ready as a Complete Player yet to really make that push.
Some find it just fine to take 1 Champion as high as they can go, and I don't fault them for that. To each their own. I just want to be a Gold+ Player, not a Gold+ Champion. I'm not good enough at ALL ROLES yet to do that, so here I am, still at Lower Levels.