Yes, I know, and that came to be my build for the robot. But it still doesn't make that much of a difference, on top of the fact that there's absolute no guarantee that you'll get any equipment (which is basically only those two that you mentioned with maybe two other ones?) that gains from the alt always on full.
With 50% more life, and even with that rule, enemies still have a chunk more life than you (in fact, not taking this rule, puts you into further disadvantage most of the time), then they have double the equipment, which makes it so that enemies that usually have smaller and weak or powerful but not many pieces of equipment (there are few exceptions like the weather changer and Crystalina that don't benefit from double equipment), have a pretty consistent chance of hitting double, and are more likely to be able to do so because they have extra dice! That small advantage of having a little more life instead of an alt becomes minuscule compared to the three colossal advantages that enemies have after the 5th floor. These advantages not only makes the enemies harder to kill and more dangerous in damage, but it also makes most of the elemental effects useless, boiling your strategy to raw damage most of the time. If you freeze one dice, they have tons more, same with burning dice; if you shock an equipment, they have the dice and also an extra equipment anyway, same with weakness. Only way to get anything out of status effects if you waste on the same equipment or those very rarely seen "all dice" or "all equipment" instances (like in gadgets). On the other hand, enemies that use status effects, because of all their attacks and dice, end up inflicting tons of them to you.
Like I said, it's just too stacked against you to get any sort of fun out of these rounds. I've manage to beat them only through save scumming when I feel like I've finally made a good worthwhile build and then fighting the last enemy before leveling to level 5 100 times over until I get good luck and they get bad luck.
The one thing that has helped me, that I didn't realize in the first runs (it gave me some motivation to keep playing after I wrote the last comment), is that you can skip a fight with level 5 enemy, in fact, you should skip one since you would want to level up before the boss and have full health. This did make it easier for me, normally skipping one in the 6th floor and getting some health from the next level before the next fight. Knowing this made the levels slightly less frustrating and unbearable, but I still feel like these get unnecessarily too hard most runs.