kilpatds
Explorer
At level 5, you're getting around 3 attacks per round with the stereotypical Barb5 GWM. Two from attack + extra-attack feature, one bonus action attack from the fact that you either crit or killed something with those first two attacks. (Alternately, you add Polearm master "just to make sure" you have a bonus action attack, but lets assume you're not that flush on feats and/or want some stat boosts). 1d12 (or 2d6) averages around 7. +4 from strength, +2 from rage, +10 from GWM. 23*3 =~ close enough to 70 to round off. (~45 round one, where you had to rage as your bonus action. 70 round two+, because you're pretty sure to kill something)
You hit because you reckless attack (and you reckless attack, because dead things don't get advantage). And you hit because after the first time you do this, the party cleric goes "Oh yeah. THAT'S why you keep asking for bless!" after the first time you do this via dice luck. I'm ignoring misses here because that's not what he was talking about.
The 120 number is Barb2 or Barb3/Fighter 5+. Basically the same, except that now you also hit via Precise Attack, and maybe throw in some expertise dice for damage ("prone") too. Action surge for 5 attacks @ 23 damage: 115. 120 if you added an expertise die in there. You'll notice the level 5 build doesn't transition that cleanly to the level 8 build... so in practice you either do an "LFR rebuild" somewhere or you temporarily fall behind where you'd rather be from levels 5-7.
So that's where those numbers came from, and the caveats. (ignores miss chance. Assumes the bonus action attack always triggers). But since I've played with one of these and run for one of these: the "70 every round, 120 nova round" number sure is a pretty accurate description of what it feels like.
You hit because you reckless attack (and you reckless attack, because dead things don't get advantage). And you hit because after the first time you do this, the party cleric goes "Oh yeah. THAT'S why you keep asking for bless!" after the first time you do this via dice luck. I'm ignoring misses here because that's not what he was talking about.
The 120 number is Barb2 or Barb3/Fighter 5+. Basically the same, except that now you also hit via Precise Attack, and maybe throw in some expertise dice for damage ("prone") too. Action surge for 5 attacks @ 23 damage: 115. 120 if you added an expertise die in there. You'll notice the level 5 build doesn't transition that cleanly to the level 8 build... so in practice you either do an "LFR rebuild" somewhere or you temporarily fall behind where you'd rather be from levels 5-7.
So that's where those numbers came from, and the caveats. (ignores miss chance. Assumes the bonus action attack always triggers). But since I've played with one of these and run for one of these: the "70 every round, 120 nova round" number sure is a pretty accurate description of what it feels like.