Not to be all DnD stat nerd over critical role but Vex and Percy’s HP.
Vex has a CON of 10 and 143 hit points at level 20. That means she has adds no CON modifier to her hp. So she rolled on average over a 7 every level. Since the Ranger hit dice is a d10, that’s slightly above average.
BUT Vex is not a full 20th level Ranger. She has 7 levels in Rogue. The Rogue hit dice is a d8. Which makes her average 7+ roll for hp even more impressive.
Percy however shows that Taliesin had all the dice luck in Campaign 1.
Percy has a CON of 14 and 202 hit points at level 20. That gives him a CON modifier of +2, meaning 40 of his hit points are from his Constitution and the rest are rolled.
Percy is a single-classed fighter and the Fighter hit die is also a d10.
Dividing 162 by 20 gives an average rolled hit points of OVER 8 for Percy.
Meaning, Taliesin rolled a d10 TWENTY TIMES and his AVERAGE roll was an 8, 9, or 10.
EDIT: just remembered that you get the full value of your hit dice + CON as your hp at level 1.
So Vex’s average roll is (143 - 10)/19, which comes to 7 exactly. Above average, especially considering her multiclass.
Percy’s average roll is (202-12-40)/19, which brings his average down to 7.9. Still very impressive, but not as broken as first thought.