MHXA team comp

I also rolled 4 tix and got her to my delight (same thing happened with Dantes). While on paper they work together well, I would go with something a little more sustainable. Personally I plan to try her with Jack and Scath. Jack to generate the stars for the team, Scath and MHXA to play with the weights and CRIT/NP Hard. The problem with Dantes is that both him and her (as well as Jack to a degree) have no star weight meaning you are leaving all 3 of their best attributes (Heavy Critting) on the table for RNG. With Scath you have some survivability, a targetable quick boost when you need and you can shift stars to her or use MHX's skill to shift stars away from her. Okita is the last one I need to get all the top tier Quick servants so I plan on mixing her, dantes and Scath around and seeing who deals the most damage.

Personally I'm taking advantage of her various traits and focusing less on her deck.

I'm adding her to my dragon team to make a standard front line of Jeanne Alter, Elizabeth Bathory, and MHXA.
Jeanne Alter's charisma gives +40% attack to dragons (which both Liz and MHXA are) while Elizabeth Bathory's charisma gives +40% to all other female servants.
MHXA's own charisma ability gives another +20% attack to the whole team to basically have MHXA at +100% attack 3/5 of the time.
MHXA's same ability is also used to decrease Liz's star absorbtion, which combined with MHXA's own terrible star absorbtion means that Jalter actually gets the stars she needs to pop off on buster crits, especially since both Liz and MHXA's double quick cards supply those stars (supplemented with 2030).

So basically together they allow Jalter to be a crit machine while MHXA has an extreme damage boost behind her spamming NP, and Liz is there to help that happen.

Of course this is a very specific set up and I'm not sure if you have a Jalter or a Liz, but in general I find having one quick servant providing stars for a crit spamming legend (Jalter, Emiya, Lancelot Saber all fall under this category) is better than just having 3 quick based servants. Jalter is just ideal because of the insane damage buff she gives MHXA.

A MHXA/Jack/Dantes is lacking in any team skills/NP charge/healing/DEF buffs. Plus there's just one self ATK buff so very little multiplicative stacking. You'd probably be relying on crits for most of the NP charging, but with only 3 Arts cards between them, you'd probably have quite a few turns without being able to lead off with one to boost the quicks.

I'm going to guess it wouldn't do really well, but I'm not really all that up on quick teams since I don't do them, so I might be wrong.

Grab Merlin as support if you don't have him and Mash. His continuous healing with her first skill and mash will allow her to live, and her 3rd skill should give her a chance to crit, while hero creation will make that turn super strong critical damage.
Until Skadi, Quick support is inefficient. And MHXA should get her 2 skill upgraded in only a few months.
Pretty much everything works with Mash+Merlin+DPS though. It is the most broken team at the moment.

Dantes + MHXA + Jack is viable but not as effective compared to DPS + Tank + Supp or DPS + Supp + supp/semi supp.

You got Caesar and Alexander on your Chaldea, they're good Quick members.

Caesar - Atk Up + NP Strength Up + Crit Up + Crit Star gen Up + low CD, your choice mate ?
Bonus : his Bond CEs increase your party Quick effectiveness for 15 % as long as he's on the front.

For Offensive buffer, Caesar is your number one.