It seems more a issue of poor design, rather then "the area is dangerous:, adding one more heat wave to bridge the gap or 2-3 more in the middle would of avoided the illusion it was designed that way to allow people to reach the small ruins with loot, or the NPC corpse (not sure if the corpse was intended to be there or a npc who ran for some reason and died there).
We took ample caution, potions of elemental protection, gear with saves and protection vs fire, and even testing the barrier to see if it was something manageable before attempting to pass the opening to retrieve the corpse on the other side of the barrier.
Even if our deaths of dismissed as "should of known better", may be worth it to bridge the gap and add some more heat waves to the open area to better represent its actual danger.