The problem with "Instant OFF GCD" abilities makes combat feel less rewarding.

[Blimbeard]

Please share with me a specific scenario where it's impossible to interrupt an ability with either an off GCD stun or Silence due to the animation lock. I'd love to hear it. And whatever you come up with (if anything) I can assure you I can give you advice on how to make it work.

Also share an example of RNG spike damage that's impossible to anticipate and results in a death purely because your benediction didn't go off the exact nano-second you pressed it and not because a tank didn't use a cool down or the ball was simply dropped healing wise somewhere.

You're missing the point completely. Instants such as those mentioned are by design reactive emergency abilities. Making it so that success is dependent on predicting scripted encounters through repetition is simply boring and uninspired when compared to being genuinely based on fast reactions during a dangerous moment

If this is intended, It's a very dull design.