So, I started playing Invoker a few months ago. I was one of those assholes who first-picks a hero in All Pick immediately and called mid. I muted everyone on my team because I decided I'd focus on improving my play and not give a fuck what people thought or said to me. So far, I've played 150 matches as Invoker and have a 68% winrate, 5.49KDA in (mostly) solo queue and have risen 800 MMR points (from 2900 to 3700). I'm still winning far more games than I lose. I'm now thoroughly convinced the easiest way to improve your MMR is to simply
get good with a farming mid hero. If I play support, I'm betting on my teammates being able to capitalize on my rotations -- to notice when I'm moving to gank and react appropriately. If I play safe lane carry, I'm betting on my support's ability to create space and keep the heat off of me.
My potential game impact is determined by how well my teammates play. If I play a farming mid, I just need to be able to outplay the enemy mid to get crazy farmed. All I need to do to secure an advantage is farm fast. Here, my potential game impact is dictated almost entirely by my own ability. By the time I leave lane, I should have enough items to snowball, regardless of what my teammates have been doing.
I usually play exort Invoker and farm like crazy. I rush a fast midas, BoTs and Euls and splitpush from 15 minutes +. I don't gank (except with sunstrike) -- the gold and experience I can get in lane is much more reliable, and chances are my teammates won't react properly anyway. I take towers to get my teammates some gold (who, most of the time, can barely get 2/cs a minute) and can TP into any teamfights and at least force the enemy to disengage. Thanks to Midas and nonstop farming, I'm usually 3-4 levels above anyone else on the enemy team.
Sending a farming hero mid, like Invoker or Shadow Fiend or Naga Siren or even PA (but for the love of god please don't do this in ranked unless you've done it before and know what you're doing) places a huge responsibility on that mid player. He's not going to be creating space for his team until maybe as late as 20 minutes in, and as such, you need him to secure an advantage successfully. If they get shut down, if they lose mid, then it's basically GG. When I play Invoker mid, I just pray my teammates don't feed faster than I can farm. I very, very rarely lose mid at my MMR, so this is the strategy that I've found to work best for me. I'm curious what MMR it'll stop working at. I haven't played Dota much lately (usually two or three per week), but I'll probably get serious about it again sometime soon. Games are definitely getting harder -- enemies are CSing better, the opposing mid isn't a complete pushover 100% of the time, etc, but I can still consistently pull out a win. There are some losses here or there, and some of them are certainly my fault -- if I'm off my game, or whatever, playing sloppily, etc. But I win the majority. Typical page of Invoker matches:
http://puu.sh/9M8tM/f7e85ac45f.pngDisclaimer: I've only played 900 matches of Dota 2. Playing a farming mid hero isn't the only way to increase your MMR, it's just what's worked best for me. I literally hovered between 2900 - 3100MMR when I picked my hero to suit my team, and in just over two weeks I increased by MMR several hundred points by insta-picking the same hero and always taking mid.