Limiting people in this way is a horrible idea. A better idea would be to revamp the dungeons themselves to add more creative difficulty rather then make you take 50 more damage, which doesn't make content harder, it simply makes it longer. In a game where anything but Coil/HM Titan is pretty tame on mechanics/depth yet filled with artificial fillers to make it longer then it needs to be, this would only add to the problem of long repetitive content inflation. Dungeons would still be boring and still take a long time, thus depriving players of their goal (to get better gear and feel powerful, this is a gear treadmill MMO like most of the others, anyone who plays has to accept that) and would ultimately have people dropping their subs.

I say no.