When certain quests or boss fights take place in an enclosed arena with limited cover. Not all characters can handle these fights and there's no way around them, like high vantage points or flanking routes. I think I'll have to change Mordecai's skill tree for these fights then change it back to its long range capabilities. I just tried one of them with Brick and he just walked all over the enemies, because that's what he's built for. I know that Mordecai isn't MEANT to fight close-quarters like that, but the game doesn't give you any other option when these fights show up. They're no problem at all during the first playthrough but they're a paaaain to beat when the enemies are Level 50.