As a porc lover in FFA, I can categorically state that while flea is strong, it is not OP.
People are simply not respecting flea and building their porc wrong. Lotus is very useful against flea and you need to build them in chains. You also need to place weaker porc behind stronger porc. Something like Razor on the outside, Gauss behind those and a combination of Lotus and Faraday behind those. Even clouds of fleas struggle to deal with overlapping porc arranged like this.
Other ideas are setting up energy pylons and Snitches as wave breakers. A single energy pylon can destroy wide swathes of fleas. I've also noticed that if you can channel fleas into narrow streams, things like Stardust absolutely mallet them.
Now, I guess I haven't mentioned units yet.
If you MUST use units, then I suggest making Fleas.
They make great border guards and provide intel on enemy positions.
They can be used to swarm ill-defended strongpoints and be used as cheap probes to find weak spots.
Furthermore, if you build 10000 of them, the players with anything less than a supercomputer are forced to drop out due to unbearable lag. Win!
*(This post written part tongue in cheek ;) )