Just ran into this bug yesterday while playing. Couldn’t finish the mission as my whole team dies from psychic attack before I can complete it. Luckily I saved before I entered the final section where the attacks begin. I hope they patch it soon.
First of all, it appears that it is only supposed to affect units within 5 tiles. However, it is reported that it goes beyond that limit. Second, if it’s not psychic damage, why is it that appears to be that the Mark is projected psychically and not physically? It appears that in their fix to insure that it now causes damage, they recreated the acid solution and crossed all boundaries. I’m not suggesting they undo it, but that it at least fits the rules.
Whatever the last boss has as an ability, there has to be a way to counter it. Mind control, can my priest block it? The damage now starts right when I enter through the large archway. By 6 turns into that area my team is almost completely dead (taking 20-60 damage each turn)unless I have a lot of medkits available. Which I don’t if I’m carrying a lot of ammo. If the hardcore players want it, then turn it on at the higher difficulty levels. I’m just a casual player, having fun with the missions, as I get to the last battle. I want multiple ways to win and not a puzzle where I have to figure out the right combo of soldiers and inventory items.