I think that there are a couple things that you can take into consideration and then ultimately work on. To answer your question: it depends.
If you play mostly Hog/Moira, I think you can carry yourself pretty quickly given some time and good game awareness. Tank/Supp are generally positions rarely readily filled, so you can focus on developing yourself as a tank/supp flex.
Its GOOD to be fairly familiar with at least 1-2 characters in each role type. Whats even better is knowing how to react to different team compositions. Hog/Moira, etc. are not always good choices, but given the opposite team composition and your own team composition, you should be fairly comfortable choosing something that will fit in.
I've carried myself by primarily filling (mostly Supp) to masters. In that time, I flex to DPS/Tank if the other members of the team prefer to play supp.
The other side of this strategy is... If you have really good aim. I mean, good CONSISTENT aim, try and play a hard dps carry like widow/tracer/cree and you should be able to soloq your way to at least diamond.