How do I climb consistently

Currently 3,1k and I seem to be forever stuck at this exact mmr. Seems like the 1 millionth thread about "my team so bad, can't rank up" and maybe it is, but i'll post anyway. Ok, so I'll begin by saying that I am not having bad teammates like most plebs out there because for every bad teammate, probability dictates that I'll always get a good one right after so that's not really a problem for me. Also I'm low-ranked, so it's best to assume that nobody in my bracket plays his hero properly.

Now this is the problem. I don't know if it's limited to 3k hell only, but something always happens every other game that is 100% out of everyone's control. What are they? Raging players, feeders, boosters, trashy draft(mirana, pudge, sniper, ogre offlane). When this happens, it's always a 70% chance that we will lose. No matter how good I or my 3 other teammates play, the lack of a 5th man will eventually fuck up our game. Note that I already did all the shit BSJ asked to do. Shove in waves, not fighting near towers, being aggressive when I can, all that stuff. The thing with watching smurf games are that they will never be behind, so that fact alone opens a lot of doors for them to play the map. What can I do or what heroes should I pick to guarantee a 100% winrate no matter what happens in my sidelanes? WHAT IS THE TRICK? Some heroes I found to be well-balanced are bristleback, lesh, puck, and invoker. I main midlane by the way.