Help with team composition

Well, for Camelot you pretty much need to be constantly switching up your party based on the enemy classes, so no one will be able to give you one perfect party that can clear everything.

That said, you have some very handy servants (I assume they're all leveled to around 65 at least) and you should be able to comfortable clear Camelot if you switch to units with the proper class affinity.

This site has a great guide if you feel like using it, if not the in-game displayed enemy class should (usually, only usually) suffice.

How did you get destroyed (no sarcasm meant), is it by high HP mobs, by bosses? Your servant line-up looks pretty good tbh. You should be able to clear the generic mobs w Cat and Heracles/ Cu alter.

For the bosses, you got euryale to take on Gawain, maybe bring an arts support like Mozart or borrow a friend Tamamo. Tristan fight can be overcome w Rama as dps and tank support like Mash or George (make sure you max skills them). For Lancelot, you can use Cu Alter, or you can also borrow a friend Avenger and use your own support/tank to keep it alive. You can brute force Mordred with Cu alter and Herc, with a support with party dodge/invinc buff like David or friend Jeanne.

I got no recommendation for final boss fights...almost died myself and resorted to turtling with Deon, Waver/Mash and a friend Okita

You need more support servants. Invest in leondias as he can bring stability and more offensive utility. Pair him up with nightingale helena waver and bring kintoki rider sanzang cu alter herc rama etc for damage. For the supports you have you might want to raise a buster archer like ko gil and buster assassin like jekyll