Those prehistoric magical beasts were some of the top prehistoric magical beasts that belonged to the same era as the terrifying existences like the ancient wyrms and the Titans. Hence, the dungeon with the gateway to the prehistoric times was definitely the one of the dungeons with the highest rate of deaths in the Endless World.
However, if there was really a team in the dungeon in contrast, they would obtain huge gains even if they simply stayed longer in the dungeon. Aside from being terrifying, the beasts' bodies were filled with treasures, and as long as a team could kill a prehistoric magical beast, it would be akin to obtaining a gold mine.
