People don't play plate frost because of the damage, plate frost hits hit like wet noodle. Plate frost is a thing because of the CC which is amplified by plate.
You see many different variations of frost because it has both CC and kiting capability. Think of a bow and a hammer into 1 weapon. That's frost.
I don't now why your arguing against something easily observed in the meta, and by just looking at the statistics for the weapon.
Firstly, all blink are not instant. You can test this yourself by walking in tandem with another players then repeatedly casting blink, the advantage you get is less the blink cast range. That's because while you blink the other person keep walking.
If it wasn't instant you literally wouldn't be able to iframe the damage of a claymore. It would be mathematically and factually impossible.
That's not iframing the spell, that's evading the charge hit box, meaning you've already moved away when the claymore arrive.
If the claymore charge has already arrived when you are still casting blink, which is not instant, you block the damage, but stunned.
This is how the damage immunity during blink look like: youtu.be/ezzCwfFU7YU?t=230
Regardless of semantics used Blinks ARE IFRAMES. This is a fact not an opinion, THE VIDEO YOU POSTED CONFIRMS THIS BTW.
Not only that but you can use blinks to iframe broadsword E, which is not based on target position, but the actual hitbox of the target .Which is why a broadsword can hit u with its e spell even through wind-wall after its casted, firewall, solid walls sometimes, and even hit you after being pushed by robe of purity. AND yet blinks can avoid this damage. Further proof that it is an iframe despite the obvious.