In addition to the named PH having ridiculously high hitpoints, the PH's also are inexplicably immune to root spells, mez spells, and pacify spells. Additionally, I've been a part of numerous hunter raids where the names are extremely rare, especially Shak Dathor Overlord. Bad enough it takes nearly 4x the damage to kill a PH, but the EXTREME rarity of the named is like adding insult to injury...
SDO took me 7 hours (during the 50% bonus), killing a 250m hp every 80 seconds pretty much continuously. Guildie is at 10 hours with his box group now, still no spawn. In addition to SDO, any named with 10+ PHs need a boost to the spawn rate as well, its unreasonable to assume all groups can keep this many down before respawn at the same time. The abandonment of the 3 PH model means that spawn rate calculations really need to be reexamined.