Hm. Well, nice to meet an actual designer on these forums, but I still respectfully disagree with your approach. Sorry if I sounded hostile earlier, most suggestions in these parts are usually made in some kind of bad faith, and at least you're consistent in your reasoning.
Maybe instead of looking at Firebolt in a vacuum, we should consider all of the other cantrips too? I think one of the other formerly unvoiced issues I had with the firebolt suggestion in particular was how it'd basically invalidate the use of most other cantrips, and the differing amount of value we place in the source material.
For one, I would prefer to be closer to the source material by simply reverting enemy AC and HP back to something closer to tabletop, and knowing that DnD largely runs on a cost/benefit analysis system more than anything else. But if the developers continue insisting on the lower AC/higher HP design, player damage probably does need some kind of buff somewhere, because the action economy is currently heavily stacked against the player as it is with the amount of fights where you're grossly outnumbered on top of that (and putting far too much emphasis on controlling the high ground and turn 1-2 ambush tactics).
It is not desirable to change a bunch of spells because one is underperforming. Its a expensive, and often unneeded approach.
I think the current approach to hp/ac is good for the most part, especially if we consider what other classes role will be. Having AC lower provides immense value to defensive buffs that come from classes like cleric, paladin, bard, etc. Shifting classes in general in a way to large amounts of ac (or damage reduction) would essentially invalidate those classes. it would effectively put cleric into a "heal, damage spam" mode, as opposed to its other current options like crowd control, and buffing. This is highly undesirable (imo) and would result in such classes being more "useless" and less "enjoyable". The game needs to stay in its current direction for now, but look at ways of reevaluating some of the "rules" of table top dnd, and looking for ways to improve over all class functionality and enjoyment.
Examples of things I consider "Rules" are things like the dice rolls, AC, etc.
Examples of things I consider "rules" that should be "suggestions" are things like "if companion can be used in combat or not".
It's only enemies that had their AC nerfed, we'd have to be fighting clerics, paladins, etc. for those to come into effect.
AC exists in tandem with proficiency+modifiers, as the player levels up, gains more proficiency or ability score improvement, there is a sense of progression.
Currently only adjusting AC down and HP up has limited the impact of player-sided spells. A sleep spell from the enemy is a lot stronger than a sleep spell cast by the player (enemies have their HP increased while player HP has stayed the same).
AC- and HP+ was a quick change that left a lot of spells in the dust.
Spell save DC was untouched and is currently nerfed, attacking spells get increased success from the reduced AC, spell save DC does not. Right now Sacred Flame isn't very viable and that puts Cleric closer to the situation of being a heal-spam class.
All spells impacted need a review, and hopefully changes to the game are implemented.
Edit: I've said this before, less spells would be underperforming if the player had been given bonus proficiency instead of the enemy losing AC.
