Now that I've had some time to think it over, I really think that Heavy Duty Boots will benefit pivot and defensive Pokemon much more than the 2x or quad-weak set-up mons. The main benefit of hazards, after all, is to wear down Pokemon that love to switch in and out, which frail set-up mons are loathe to do. Volcarona, Gyarados, and now Frosmoth don't really need the HP to sweep as long as they get a chance to pull off a DD or QD, which you can really only do for free a few times per battle, after which they are likely to stay in and punch holes till they die. There's also the downside of running the Boots over another, maybe prefered item, like Lum Berry/HP restoring Berry or Life Orb.
Instead, let's look at a pokemon like Reuniclus. HDB allow it to run Regenerator over Magic Guard, while still getting alot of the benefits of the latter. From there you can run a defensive utility set. Another few Pokemon that might benefit from HBD would be Unaware Quag, Regen Pex (though it might still prefer shed shell or sludge), Sand Stream Hippo (especially with what will amount to a new weather war with Dynamax), and Shuckle.