>>528458836
The only problem is that changli buffs lupa but lupa is the least damaging by far of the triple fusion team (that also has the highest damage contribution overall due to how much buffs she gives). So there is an opportunity cost over using her with brant, but that's if you're doing the straightforward rotation without quickswap.
>>528459029
If you mean prydwen numbers, they are using a support rotation (7.5s), but S6 allows you to slam 10 times instead of 3 for sustained dmg.