I completely agree.
A) The frequency of this effect is too high. It creates an entirely aggravating combat experience that is not, in my opinion, offset by any feeling of competence once you do learn to quasi manage it. Making it less frequent would allow you to control for the effect better, and would decrease the aggravation it causes.
B) This effect, paired with certain class abilities and / or items, is compounded and made even more frustrating by the additional loss of control. For example, the levitate effect on the Humming Black Dragonscale (HBD), which is a frequent and uncontrollable proc, causes you to travel much further, particularly given any elevation change present at the time. This is not something that can be controlled well, as often in the visions, you must move out of some ground effect or mob ability. If you are unfortunate enough at the time to have the HBD proc up and then get launched by scorched feet, you will travel quite a distance with no recourse. The random and uncontrollable nature of this causes frustration and nothing more. Mechanics that are random and not (read effectively not) able to be countered are neither fun nor constructive.
While I agree in part with the sentiment that ‘madnesses are meant to impose complications on the runs’, I do not agree that simply because a complication exists, that it therefore lends value to the run. The difficulty / impact of a mechanic should be offset by manageability and a feeling of reward once it is managed. Given its current state, I believe that scorched feet is neither sufficiently manageable nor rewarding, relative to the amount of aggravation that it causes. This is not to say that it is completely unmanageable, but rather that the consequence is disproportionate to the recourse.
I think it would be easy to lessen this aggravation by simply decreasing the frequency of its occurrence, or by decoupling it from item / class effects, such as the levitate on HBD, if it were not desirable to just remove the effect entirely.
However, given the state of 8.3 and the long list of other, much larger problems (corruption imbalance, the awful essence / azerite / reputation / coalescing vision grinds, the entirely unacceptable class imbalances in pvp and M+, etc.), I’d say that the devs should probably fry bigger fish.