The national team originated from Chongyun-Xiangling-Bennett-Xingqiu (as three members are from Liyue). Over time, it has included many variants, especially with new character releases such as Raiden or Yelan. One theme of national-type teams is the use of multiple sub-dps units.
No RES modifiers. Raiden + Xingqiu (off field) + Xiangling (off field vaporization) $$494.1 + 415.2 + 397.5 = 1306.8$$ This does not factor in vapeload damage (electro charged + overloaded). It also ignores the burst dmg bonus provided by Raiden's E. Advantage of team is Raiden batteries XL and XQ's higher 80 energy cost burst, making spamming bursts on cd more achievable in practice (compared to say a Ganyu melt). This gets a big boost if the enemy consists of Electro Rifthounds (which lose Electro RES).
You can replace Xingqiu with Yelan for more damage too. (Yelan passive also gives up to 50% dmg bonus.)
VV shred from Anemo unit, ignoring damage done by Anemo unit $$494.1*1.278 = 631.4598$$ This team is not recommended for dps unless one has C3 Raiden and C6 Sara. Even then there are better options for dolphins/whales. Even Raiden national is more accessible.
Suppose Chongyun has 61.6% cryo dmg bonus and lv13 q. MV is $$302.6*3*1.616/12 = 122.2504$$
No RES modifiers. Suppose optimistically Xiangling melts every hit with the help of Chongyun's E infusion $$415.2 + 122.2504 + 397.5*2/1.5 = 1067.4504$$ It's still better than melt Ganyu. So Ganyu really fell out of the meta. Actually Ganyu was never meta to begin with since this team existed from the very start in Version 1.0.
VV shred from Anemo unit, ignoring damage done by Anemo unit $$(269.84 + 397.5)*1.278 = 852.86052$$ If we consider an extra 30% dmg bonus from Kazuha $$(269.84*2.504/2.204 + 397.5*2.266/1.966)*1.278 = 977.319492149$$ This is higher than melt Ganyu. It is around Itto level and probably higher when one factors in the damage from Kazuha. Above also ignores Childe's burst and riptide.
This is Xiangling-Xingqiu-Bennett plus Kazuha/Sucrose. VV shred from Anemo unit, ignoring damage done by Anemo unit $$(415.2 + 397.5)*1.278 = 1038.6306$$ If we consider an extra 30% dmg bonus from Kazuha for Xiangling $$(415.2 + 397.5*2.266/1.966)*1.278 = 1116.15$$ This is higher than Hu Tao team dps.
The dps from these 3 characters alone $$415.2 + 397.5 = 812.7$$ One can do Beidou national, etc.
The introduction of dendro introduced a new type of national team: the dendro national consisting of dendro, electro, hydro, and pyro. One such team is Raiden, Yelan, Bennett, and Dendro MC (DMC) or Collei. Bennett is for healing. It is possible to do Xiangling but then there is no healing. One can also use XQ but his healing is minimal.
Is there an edge of using dendro over other variants like another pyro for the fourth slot, cryo, or anemo? If anything dendro national can provide more flexibility in team building, if other characters are used on the other team of the spiral abyss. Dendro national may also have more types of reactions including the new bloom and catalyze reactions. The catalyze reaction provides another way to increase electro dmg.
$$663.7 + 494.1 + 445.4 = 1603.2$$ This is one of the most powerful national teams. It becomes more powerful with Nahida's c2 and Raiden's c2 combined. This does not factor any reaction damage, which would increase the dps even more given that this team will be doing a lot of quicken, bloom, burning, overloaded, and vape procs.