I've done bronze to masters climb several times and I always shotcall when I think it will help. Asking sonya to clear shrine, dehaka to dig top, greymane to merc, etc. I find that in 99% of the time I ask, people obey and it works. Shotcalling is easy to way to carry games, but you must ask early enough for them to actually do it.

You can also play high impact heroes. Right now, genji, nova, and valeera should be freelo at lower ranks if you truly don't belong where you are. I think heroes like hanzo, greymane, malthael, sonya, and even gazlowe or anything that can solo merc are also in that boat. Anything that can solo merc will greatly increase your chances to win games at ranks where people ignore mercs. They are very powerful now and as long as your timing is good you can get a lot of value.

I don't know if this is what you mean by carry, but I think if you just play from this hero pool and ask people to do the things their heroes are good at in a timeframe that allows them to accomplish those tasks, you can make it to masters.