First off, of all the sites I have visited in the past, I have found this one to have the most insightful commentary. I do not always agree, but people use...reasons. Refreshing.
Anyway, here is my question.
What is "good" at-will damage?
In this we have melee and missile attacks of course but also cantrips and the like.
If possible, provide some sort of cut point (your opinion cannnot be wrong in this) for exceptional at-will damage and poor at-will damage.
If you are really ambitious and want to divide this into martial damage and spell damage as well, I would be thrilled to know your thoughts.
One last moderator is level and tier...good damage at 1st level will of course not be good damage at 15th! In this discussion I think we should dispense with one time effects such as action surges or hasted actions etc. and focus on the at-will component.
Poor at-will damage: Cleric or Druid fighting in melee.
Average at-will damage: Sorcerer and Wizard cantrips, archer warriors with no feats, sword and board warriors without the duelist combat style and no feats, ranged rogues, monks, bladelocks pre UA.
Good at-will damage: Great weapon fighters, barbarians, and paladins without feats. Post UA bladelocks. Rogues with the Scag cantrips, rangers, blast warlocks with Hex.
Exceptional at-will damage: Sorlocks with hex + quickened eldritch blast. Warriors with great weapon master. Warriors with polearm master. Bow archers with sharpshooter.
Way beyond what should be possible at-will damage: Great weapon master warriors in a party that easily has access to advantage (faerie fire, stunned, hold person, etc). Crossbow expert sharpshooter archers. Great weapon master + polearm master warriors. PCs shapeshifter into CR 17 red dragons.
Generally speaking, 1d8+3 is probably the base line for levels 1-4. It's a one handed weapon attack with a 16 ability modifier, so anything above that is going to be "good" while anything less than that is going to be below average. At level 5, this will increase to 2d8+4 (assuming +1 to ability modifier or +1 weapon), and by level 12 it should be no less than 2d8+5. Of course, at will damage varies greatly, since many classes rely on limited benefit damage (rage, smite, ki, spells, etc.), while some (fighter and rogue) have no limitations on at will damage.
If you just want to look at cantrips, my group agrees that xd10 is the baseline. While most cantrips are 1d8, they come with a minor benefit (Chill Touch, Ray of Frost, etc.). Cantrips that deal less than that usually have a good bonus effect (i.e. vicious mockery) or hit multiple targets (i.e. Thunderclap and Sword Burst). Poison Spray, which deals xd12, has a VERY short range, making it less useful.
I would not put Sharpshooter + Crossbow Expert in a different tier than Sharpshooter. Increasing the die from d8 to d10 is not a significant damage increase. The feats only really worth it because of the elimination of disadvantage at melee range, and even then you don't consider taking it until you have 20 Dex and Sharpshooter.
I'd also put any Warlock with Hex and Agonizing Blast into Exceptional, not just sorlocks, because that damage quickly matches or surpasses Sharpshooter characters.
Crossbow expert isn't there to use ad10 crossbow instead of a longbow. Crossbow expert is there to use a hand crossbow and make a bonus action attack every round, increasing your number of attacks by 50% from levels 5-10, or 33% from levels 11-19. That, when combined with the +10 damage from sharpshooter represents a massive increase to damage per round.
Nothing is preventing you from dual wielding hand crossbows.
PHB p195 said:When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand.
No, you can't dual wield hand crossbows. The two-weapon fighting rules say (emphasis mine):
That's right. The Light property of hand crossbows does absolutely nothing.
That's why everybody who read Crossbow Expert said, "Oh, cool, this allows me to dual wield a hand crossbow!" Except, no, it doesn't according to Crawford. Not at all. It allows you to fire it an extra time. That's all. They just worded it so badly that you can't tell.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.