Guys, its not a trading card game. dont think your the first person to ask for trading to be available. notice at the top of the screen it says "Kongregate’s long-awaited collectible card game!". Thats right, collectible. not trading.
To beat lvl 100 flyings, you need about 15 fully upgraded swarms, with around 7 spike towers to stun them. Slow towers also help.
Also, darks dont only take damage over 15. They take a percent of their health.