So instant skills are not going off instantly - working as intended (why this then?)

[Eirva]

I understand this. I asked in free company why I would want to use Bloodletter over Heavy Shot. -snip-

Use Bloodletter right near/at the end of the GCD, then use a GCD ability immediately afterwards. The GCD ability will cancel the rest of the Bloodletter animation. It's most obvious if you combine Bloodletter and Windbite because Windbite's animation is so much different from the rest of the stand-and-shoot abilities. If you wait too long or hit Bloodletter too early, the animation won't cancel. Try practicing on one of the striking dummies. You'll need to get used to it, especially when Bloodletter is constantly resetting on DoT crits.