I Have a Legit Problem, and Riot Has the Solution
Alright, so here's my plight. I am good at two roles in this game - Jungle and Support. My mid and top are, at best, 30/70. My ADC is probably worse. When I'm jungle or support though my chances soar to more like 60/40. I like being a team player and I think that's why I tend to do well in those two roles. Here's where it gets heavy though: If I choose support as my primary or secondary role I will get it 98% of the time.
Look man, let's real talk. I don't mind supporting and even enjoy it. I also like jungle however and would really appreciate a 50/50 mix between jungle and support. If that was the case I would queue support as my secondary 100% of the time, and thus play support 50% more of the time than I do now. That brings us to how Riot can help with this dilemma.
I suggested this back when the new champ select came out, and will suggest it again. Make it so players can choose what percentage of playing time they prefer for individual roles. You might be surprised to find that a lot of people don't mind playing supports part time, but never queue it because they get it nearly 100% of the time.
The problem really arises when I'm forced to pick one of my weaker roles as a secondary because I can't pick my REAL secondary role due to the way your algorithm current works. Simplify it and let people pick a percentage of playing time for what roles they want, and I bet you'll get a boost in support queues. Let me be a jungle/support main, my body is ready.