^^ hehe, Happy Birthday
I dunno. I won't scream infestors are OP but as soon as my opponent gets them I end up losing the game If I attack before infestors or snipe their pit, then I still have a chance at winning the game. Nothing as horrifying as seeing a ton of marines just dying to several infestors, really cost efficient imo and I believe overall, the infestors is quite possibly the best spellcaster in the game.
IT: crazy good dps and it's all energy so it's a good deal either way. Had opponents use their infestors to create like 40+ IT's then take down my PF before I had enough time to react -_-
FG: Great as well, if you don't have detection(dts, banshees, etc....), you can detect the units and root them for your units to attack. That and you can just root any and all units barring ultras. No micro is possible when units are FG'd. It might not be as damaging as storm is but at least you can dodge storm and receive less damage but in this case, it's the same damage regardless.
NP: Your opponent went mech or mass tier 2-3 units, etc.... easy solution, just NP them and have them target each other while the rest of the Zerg army tear the remainder of the army in half. I originally thought that NP was a bad spell due to the time limit but I think the time limit is the only thing holding NP back from becoming OP
As for mech play, if the zerg is dumping all of its gas on infestors, u don't need to mix more than couple of thors. Get raven for detection against burrowed roach+infestor and mass helion tank.
Infestorling these days is kinda equivalent to old colosi unit composition. At the start, terrans just a-moved their army and complained colosi QQ. These days terrans learned to spread their army and colosi ball became inadequate so the metagame switched to templar tech.