I'm sorry, but the damage at which the two classes are equal is so large that a boss hitting for that amount at a frequency the like of which we're discussing would be untankable. _________________ If you shoot Anthony several hundred times with an anti-tank rifle whilst he is stabbed to death by a squad of ninja monkeys, he will be dead.
As the number of discrete attempts to hit increase, the relative value of avoidance also increases. At a certain point avoidance begins to function very much like mitigation.
Also, if the hits are spread out in time, it becomes easier to heal insofar as the timing of landing the heal becomes less problematic. Since damage is coming in so often at a smaller rate, it's likely to result in less overhealing.
These are the kinds of arguments you can make about why smaller but more frequent isn't quite equal to big and less frequent. And these arguments are valid, to one degree or another.