I have found the secret to increasing your solo MMR!

Viper.

Just don't building a f*cking Vanguard and you'll be fine.

Viper is good because you can:
-Build a Mek, which no one else will.
-Gain map control and make space for your carries by pushing early T1s and ganking a hell of a lot.
-Buy dust (if they have invis) and wards (occasionally) cause you have too much gold and don't need a lot of it.
-Is a tanking machine which most people want in their team.

Just don't play/build Viper as a hard carry. He's a good mid-game hero where he snowballs the f*ck out of control but past 45 minutes, he drops off pretty hard besides his ulti, which is why Aghanims is core on him.

All you need is Mek and Aghanims. Everything else is situational. AC, Heart, Butterfly, Daedalus are all good choices. Don't build Manta or Vanguard.