True, of course, different boss will require different matchup and probably even set tactics. Things like Weavile would have its HP bar deleted quickly by the likes of Lucario. Some mon may be walled and countered hard that simply bringing it and doing ol' beating would keel it, while others probably require more careful approach (such as antiraid-coverage-equipped Hydreigon/other offensive behemoths, things with more bulk and less exploitable weaknesses like Snorlax). Hmm... this is one interesting PvE aspect I like to tinker about. I can think of running support Vaporeon armed with the likes of Fake Tears/Helping Hand/Toxic. And, as of PokeGO, the best DPT dealer of each type.Sorta.
The showcase had a dedicated Togekiss with defensive moves and Follow Me. A setup with a defensive / utility pokemons which would allow your dynamaxed pokemon to tackle the boss more easily.
Now, that's purely looking at that one Steelix boss which appeared to be low difficulty / level, obviously, plus being a slow Pokemon it made easy to just status / punch him to death. They shown much faster Pokemon having Dynamaxed raids (like Weavile), so different approaches per raid might be necessary.
Setting advantageous multipliers would be crucial too, like setting Psycho Terrain in Psychic-weak bosses, Elec Terrain against Gyarados, aformentioned Fake Tears/other Def debuff, etc akin to a MMORPG raid with player's various classes and roles.