Yeah I know
You are close. I consider myself mid-tier as well. I don't think I do anything special. I just try like 7 or 8 things on every turn and decide on one that I think is best. That's my favorite part of this game. In chess, you can't move the piece around to get a visual idea of what the consequences will be. In Hero Academy, you can. I would suck so much if not for that.
Also, when deciding on a move, try to think how you would react to that. Do the math in your head to figure out how much your opponent can respond, and evaluate the risk associated with your move. The ultimate goal is to force your opponent to make a Sophie's Choice. Give him a couple options, all of which have a bad consequence. Something like this is great:
Kill a high value unit and leave 2+ of your units in the area to deal with the response. If he wants to heal his unit, he'll hopefully have use a turn to to move a healer closer. Then, he has this choice. Spend two turns to rez his unit and heal it, leaving him with only two more turns. This means he likely cannot kill either of your units (which you use next turn to kill the first unit, or better yet, the healer). The other option is that he only rezzes his unit, leaving him 3 turns to attack and kill (but not stomp) one of your two units. But then he's fucked, because his unit is left with probably 100 health (more if humans) and your remaining unit can kill and stop it in 2 turns. Then you've got three more turns to rez your dead unit and run the fuck away (or, if you can, keep the pressure on and really put him back on his heels).