FACT: Skills go off/fire/trigger/etc. on key release.

Ex. You press "1" to cast "Crushing Shock," your character will not cast it until you release the "1" key.

I tested two keyboards:

1. $150 Roccat Ryos MK Pro Mechanical Keyboard with medium feedback (meaning it makes a click on key press/release sort of like a typewriter)
2.$10 Patrionics Wired Keyboard (the most basic keyboard I had laying around)

Results:
Skills go off faster on the non-mechanical keyboard. The mechanical keyboard produces a delay in triggering skills.

My friend did similar testing with a Logitech mechanical keyboard and a cheap non-mechanical keyboard. The results were the same mechanical keyboard caused delay in skills triggering.

I did not macro or animation cancel, I was simply testing skills firing on mechanical vs membrane keyboard (if you open it you will see a rubber mat that maps all the keys above). The non-mechanical keyboard produced higher dps.

TL:DR

Mechanical keyboard causes delay in skills triggering which could be gimping your dps/healing/tanking