I think you're vastly overestimating the threat Dragon Claw poses to these Pokemon.
Bronzong forces the Dragonite user to Roost 2 times every 1 time it uses DD and will need to DD up to at least +4 before chancing a 2HKO, in all this time you can be hit with Toxic, Reflect, a crit, or Bronzong can CM up itself. It is Bronzong that has the freedom to do as it pleases, not Dragonite.
Jirachi is so versatile that Dragonite just should not be entertaining the idea of setting up on it with just Dragon Claw as its only move. ScarfRachi Iron Heads, Ice Punches or Tricks to its heart's content. CM Rachi, as you put it, sets up in your face. Screens Rachi uses it as an easy opportunity to set up for teammates and Dragonite will be toothless with a Reflect up. SpDef Rachi is the only variant that Mono Dragonite has a chance of defeating, and you can't use 'the opponent will use Body Slam' as an argument because you can talk anything up by saying stuff like that. You should assume Jirachi always uses the best move because you're assuming Dragonite is always using the best move and compare them that way.
Ferrothorn is much easier to set up on because wasting Gyro Ball PP is much easier especially if you Roost early, but that is again putting player skill into the equation and you can equally say an informed Ferrothorn user will know that Dragonite poses no threat until it is severely boosted and will use Leech Seed or Thunder Wave when it is at half health, predicting the Roost instead of the Substitute that will eventually lead it into a dead end.