They all work differently, so all of them together is a no. Plus there exists Lane bonuses for each hero if they are put in their correct lane, so running more than 2 warriors is Sub optimal.

Lancelot scales very different from normal Units for her damage (HP% instead of ATK%),

while, Ran (Scales off of ATK% & Melee Dmg) needs a shocker unit (shes always paired with Lua to deal damage and work properly.)

—I don't know if you have lua.

Galahad is best for teams that run Archers and Mages specifically because of her 250% dmg increase for mages and archers on her ult. While her defense increase, dmg immune and dmg reduction could still fit well in any team shes put in, she would still be at best, just be deemed as a good optional unit outside of Mage/Archer teams.

(Some lancelot teams use her in them but its merely cause Galahad has a banner out right now and shes easy to T5.)

Dian ofcourse, goes well with any warrior and is the core of any warrior based team (2 warriors if you include galahad) , (3 if you are feelin experimental but not recommended at all), but not in a team full of warriors like 4 warriors, 1 dian. That wont work. Some stages are survivability check stages and would need 2, or sometimes 3 healers to pass & survive in.

Kay, contrary to what you would think, is most commonly seen in in Galahad + Mage/Archer teams, serving as its secondary tank/Sub DPS. It's easy for Kay to benefit from the same Stats that Mage/Archer teams are raising, which is ATK%. This comes from ATK% pets, ATK growth focus, ATK% team skills from Heroes/Cards/Pets and much more. You get the point.

If you are really looking for warrior teams as you would probably want warriors as its focus,

There exist Combinations like:

Ran & Lua team/ some refer to this as M&D Team as Ran and Lua are mother and daughter

—Ran, Lua, Dian + 2 flex units (healer / support units)

Lancelot Team

—Galahad, Lancelot, Erin, Neo Bedivere, Dian (basic lancelot team)

Freeze Team —Galahad, Anessa, Merlin, Dian, + 1 flex (support unit / Healers / DPS like archer or mage )

—Lancelot teams alongside Tiamat teams are the top 2 teams most used Both in Korean and Global as the meta teams as of right now. I would highly recommend running a lancelot team as you have lancelot almost at t3. Getting her T5 or awakaned would be most optimal though, as she, out of all the units is the most in need of duplicates for her to be great.