You know Primes are retarded and don't know how to ride in Mycetic Spores, right? Be sure to read the Tyranid FAQ
Your Trygons are begging to have Adrenal Glands. AG should be considered standard equipment for Trygons unless there is absolutely no way to free up the points for it. Being I5 on the charge is absolutely huge, since it means you go before most of your prime targets, and the S7 can be very helpful when you are going after vehicles.
I would probably drop the Gargoyles in favor of some Zoanthropes in a Mycetic Spore. They help a lot for dealing with those pesky AV14 vehicles and would keep with your DS only theme. Besides, 20 models is a very huge blob of bugs that would be extremely risky to DS with. Keep in mind that they don't have scatter correction, and if they mishap, you could easily lose a good chunk of your army, and we need every last bit we can have.