Umm, no, you DPS through it. If you do not DPS it down it goes back up 2 seconds after it drops. If you DPS it down, some damage gets through AND you damage it dropping it sooner. It is a scaling mechanic, more people, bigger shield, effectively increasing the bosses HP based on how many people are currently there.
It is not a reflective shield, there is no harm done DPSing during it. It is Reactive, reacting to the number of players in the area. Stopping DPS during the shield just prolongs the fight.
Other than that, I basically agree with you. I am not a huge supporter of them yet, I just do not understand this negativity directed towards what is an enhancement of the old Expert Rift system and provides opportunity to expand and varying levels of challenge. It also affect Raid Rifts which still exist in no way.