First of all thanks for the highly detailed response! I don't have a long time but a few things stood out to me as a bit odd.
Even with a vicious weapon and all attacks hitting 100 hp of damage seems high for a valor bard. 1d8+2d6+5 per attack. Then 1d8+3d6+2d6+5 per true strike. That totals to 70.5 for 2 true strikes and an attack. Rolling extremely high could hit 100 damage but is extremely unlikely. Is there something else other than the vicious weapon really boosting the bards damage? I mean even the combat inspiration ability is at most adding 3d12 = +19.5. What am I missing?
Fighter is only doing an average of 19 per attack with a vicious maul. That's maybe 38 damage on those 2 attacks (a bit more if he crits, which he has a really good chance to, but still). A normal earth elemental has 126 hp and possibly resistance to the damage depending on 2014 vs 2024 version. These are supposed to be stronger. I'm having a hard time seeing how a champion fighter kills one with 2 attacks. What am I missing?
THL is great now. But it didn't have much of a huge effect on this encounter. Enemies died too fast, and seemingly faster than they should have.
That's not how fear works. If they have no where further to run they don't lose their action even if they can see the caster.
Fear
"...A Frightened creature takes the Dash action and moves away from you by the safest route on each of its turns unless there is nowhere to move..."
Maybe more thoughts later, I have to go for now