Errrr Nope, they don't crit, atleast not unless its a specific mechanic. I'm 99.9% sure on that, but feel free to provide a source saying otherwise.
If RNG shouldn't be able to dictate your effectiveness then surely, to make it fair, you shouldn't be able to crit your attacks or heals either, then?
And no - If things are balanced around raids, that trickles down to 4 man dungeons and extreme trials....but it doesn't work the other way around.
Well no - Checking for crit first is how the game works. If its a crit, it wont miss, and it'll do more damage.
That's simply how the game is coded and it makes sense.
Is damage crit? Yes
Did target block? Yes
Take Crit damage number, reduce block percentage, apply damage.
It should not be Reduce block percentage, take crit number, apply damage. That's not how even basic maths works.