About David...

Yes, yes, yes. David is an AWESOME support archer. He gives the entire team a one hit dodge and many other benefits but I’m not sure of what they are, I don’t use him

I lucked out and got Tristan, but had that not happened I probably would have had to go back and level David to get past Guwain and Mordred in Camelot.

Archers with a group evade make those bosses ALOT more manageable. At least till the lion king shows up with her pierce invincibility...

David is a really, really good servant.
He has survivability for himself with the heal+def up, he gives an awesome support tool with Harp of healing, removing mental debuffs (such as charm), healing a little and 1 hit evade, and a good Charisma, which is always welcome, then his NP has sure-hit, deals a pretty nice damage and has skill seal.
Also, his deck is good for arts-chain for faster NP up, and has one of the highest ATK in the 3 stars lineup.

You really should level him up. No Master is good without David.

Yup, definitely a great 3-star. Teamwide 1-hit dodge + heal, self-defense buff + self-heal, and teamwide attack buff for skills, plus decently hard-hitting single-target NP means he covers a lot of bases and gives you quite a lot of freedom for team comps. His 3 Arts cards are also pretty useful to help in raising his and his team's NP bars faster.

He's pretty much the only non-gold support Archer on the NA server right now, and is better at it than most higher-rarity ones (of course, gold Archers usually compensate in other ways, mainly damage output). As long as you're careful not to put him up against too many Lancers he'll serve you well.

Well, he is a great unit and ''good'' is not enough to describe him.

Raising him will gives you a lot of benefit, best used when you're having hard times dealing with harder contents and challenge quest.
There are still lots of untold stories or tales about how good he is.

I cannot vouch for David enough, I use him all the time including during the Solomon raids and the nero fest challenges. Great utility that can even throw out a strong np when needed.

David is wonderful while still building your servants with the team evade to protect you from boss np's. He saved the day many times in my early days of FGO. Now that I have a lot more maxed gold servants I have a much higher likelihood of clearing quests before the boss charges np, so David isn't used nearly as much anymore.