Double digit level. Even 11th. And no, I do not buy that fighters are dealing that much damage. There's just no way they can. At best, the absolute best, a fighter can do would be a 2d6 weapon, with something like GWF and a 20 Strength. That's as good as it gets. That's 27 damage per hit. Oh, wait, sorry, add another d8 for Battlemaster maneuvers. So, 35 damage on a hit is the absolute top.
At the absolute top end, there's 5 attacks for 175 points of damage. 350 if he action surges. So, that is the absolute best damage a fighter can do.
A wizard can do that at 5th level. Fireball hits 10 targets for 35 points each. Poof. The absolute pinacle of damage that a fighter can do is equal to what a wizard can do at 5th level.
It doesn't have to be "round after round". There's only a limited number of rounds in an adventuring day because the baddies die.
Again, as I said earlier. Track it. Actually do the math. Track your next 20 rounds of combat. Area attacks deal total damage, not single, so, it's not fair to compare a single target - you have to talk about total damage. I'll bet you dollars to donuts that your casters are number 1. Every time.
I mean, why stop at 10 targets? A 20" radius sphere could fit a LOT of tiny creatures, so if we are making an argument around the hypothetical damage a character with access to fireball could do, we could get it much higher. But what is the point? That against a ton of weak opponents in a confined space fireball is incredibly powerful? You'll get no argument from me!
CritRoleStats actually does track the damage done by every character on Critical Role:
Campaign 1 (115 games, levels 7-20)
1. Barbarian/Fighter (Grog): 10, 038
2. Rogue/Paladin (Vax): 9, 183
3. Ranger/Rogue (Vex): 8, 514
4. Fighter (Gunslinger home-brew variant) (Percy): 8, 126
5. Druid (Keyleth): 6, 126
6. Bard (Scanlan): 3, 334
Campaign 2 (141 games, levels 2-17)
1. Monk (Beu): 5, 965
2. Warlock/Paladin (Fjord): 5, 614
3. Rogue/Wizard (Nott/Veth): 5, 583
4. Wizard (Caleb): 5, 281
5. Barbarian (Yasha): 4, 750 (
note 32 fewer games)
6. Cleric (Jester): 3, 648
Campaign 3 (51 games until party split, levels 1-7)
1. Barbarian (Ashton): 1, 462
2. Fighter (Orym): 1, 392
3. Sorcerer (Imogen): 1379
4. Blood Hunter (home-brew class; similar to fighter) (Chetney): 1, 222 (
note 6 fewer games)
5. Druid (Fearne): 858
6. Warlock/Sorcerer (Laudna): 762
7. Cleric (Fresh Cut Grass): 567