Been running into an ice-wall lately with my Invoker spam. What am I doing wrong?

So I've been spamming Invoker recently to try and learn the hero (probably not the best hero to learn at my current skill level but I just can't stop spamming him).

I played this match which I feel is somewhat indicative of the problems I've been having with my play: http://www.dotabuff.com/matches/2293936772

I feel like most games I do reasonably well in the laneing stage relative to the enemy mid and sometimes even net a few kills with some sunstrikes. But as soon as the midgame comes around it all seems to fall apart and oftentimes the enemy mid will become very active and snowball off of ganks and towers while I feel powerless to help. Am I playing too passively and farming too much? At this point I'm not even sure what the right questions to ask are.

Any tips would be greatly appreciated!