Finished Season 2 on both normal and hard (270/270). Not having many high leveled Atlantis heroes grabbed from the Summons ensured that I am mostly sticking with clearing these levels with Classic Heroes.
One of the highlights from the S2 stages are each of the provinces featured special stages (Poison/Magic Night/Misty Forest/Underwater), as I progressed through the latter provinces that had the Underwater stages, I had wondered, would certain S2 heroes fare much better in these stages? Having only Mnesseus and Melia for the Atlantis family on my roster I dared not try and especially not on the higher provinces, one day I just decided to wing it (I am still working on the underwater stages mission) and just put both of them in one of the earlier, less scary underwater stages on normal and tried.
When I see the Mermaid and Merman of Atlantis taking damage from Low Oxygen and gasping for Air… I’ve seen all I needed to see. Why the heck are Mer people who predominantly live underwater take damage from low oxygen??? By this account, Ariel and Poseidon, Gods and Demi-Gods, also would take water damage in these stages.
I don’t think it will be very game breaking to have Heroes from the Atlantis family, if they are on your team, to not take HP damage while in Underwater stages. Similarly, have the heroes from the Lagoon Family not take damage from Poison stages (perhaps they have natural defense from prolonged exposure to the toxic swamps) or the Sakura Family members all having special lanterns/amulets that allows them to see through the mist so the Misty Forest stages do not affect them.
Since these special stages are not featured in P2P situations (War/Raid/Raid Tournaments) and only during story campaign, the enemies are not subject to the same handicap, and again, not everyone has or uses S2 heroes, I think it is a pretty good perk that the season 2 heroes do enjoy a certain perk while in certain stages. Again, the Atlantean heroes taking lung damage from underwater just makes no sense to me.