A for concept, D for execution
This is an excellent idea for a game. Mix the aspects of a puzzler with the strategy of a lane-based combat system. The fact that the puzzles make it difficult to execute the strategies is the entire point. The idea of using the puzzle to add some spice to an essentially-dead genre is a brilliant idea.
It's marred by a few problems in execution, though. For one thing, the grid is too small. I understand the necessity of making the grid that small--it allows you to identify the sprites. But if there was any way to expand the grid, do so. The second thing is that using sprites as the things you have to match is an interesting idea, but the sprites look too similar. I think it's because the sprites are all humans, and therefore must all have human features. I understand that there's not much you can do about this either, but I'd suggest replacing the sprites with symbols that represent them. There's a reason Bejeweled uses brightly-colored geometric shapes--they're easy to tell apart.
Finally, there's no strategy involved! You toss out whatever matches you can find, hoping pathetically to keep things flowing before the enemy castrates you. Next time, implement a lane system, so that players have to manage both the act of getting troops onto the battlefield and the lane-based combat system implemented by other games. Now THAT would be a challenge!
All in all, a great idea, but there were too many problems for it to shine.