Dark Templar are for people who are smart. Not for people who are dumb, and make 12 of them like a fucking asshole.
You drop DTs at 7 mins, send 2 at main, 1 at expo, take down workers at expo, split the 2 in the main to hit high priority targets (workers, tech). This way, no scan, can kill all of them at once, no Overseer or Observer can keep tabs on all of them at once, and they inflict the most damage possible.
No one, and I mean no one, in their right mind would make 12 DT and use them in a frontal assault, sure it would do some damage, but it would be all-in this early on, (12 DT is 1500 min and gas), and would likely make you lose the game.
I talked to a Master about DT Expand the other day, and he detailed his strategy for using them. He said he uses them more than anyone else in Master league, but he told me to never get greedy with them, it will cost you.
And it's not Dark Templars, Templar is already plural, you wouldn't say Chineses.
Stick to playing Zerg.