Cursed Ground sometimes fails

A curse with Cursed Ground Support often fails to apply, despite mana being spent, if the designated area is not WIDE OPEN terrain. And as we all know, wide open terrain is a luxury in this game, so I'm constantly running into instances where my curse fails to apply multiple times in a row, leaving me with no mana to cast spells since curses cost a colossal amount of mana, and having to use mana flask and wait for mana, often putting me in dangerous situations.