Rethinking things through, I don't agree with the average Herald being "3-C normally, 2-C at peak". They don't have a mechanic where they go from one tier to another by putting more effort into it. If they are already not holding back, most context they're in should already make them be at their peak, be it a life-or-death battle, saving a lot of people, being angry, or being stated to go all out. What context would make them jump from 3-C to 2-C mid-battle? Nothing that wasn't already there, and if they were fighting another 3-C how are they not annihilating with this tier jump they have but the opponent doesn't?
It's worded wrong. "3-C, likely/possibly 2-C" or "3-C to 2-C" makes far more sense as it means 2 average Heralds fighting w/o holing back are at the same tier (3-C or 2-C), w/o any 1 of them or both being able to jump into yet another tier mid-fight.
Now, Thor does jump into another tier via enough effort, but that's his own personnel thing and most of the time he does similar efforts and doesn't jump his tier in any context (like going up against other Heralds w/o holding back).