Dark Templar rushes never work in higher level leagues, because all good players scout early and scout often. They can smell a Dark Templar rush comign from a mile away (once they see that tall Dark Shrine), and can build inexpensive ways to defend against the squishy Dark Templars.
If someone DT-rushed me, I'd be more than happy to sit there quietly while they throw all those resources building their useless units.
I wouldn't say they are useless, but yeah it's GG if they do it against me. If you can take out their observer it's a great defensive unit.
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