Mana Tide Totem used to stack multiplicatively, which means that if one totem doubles your mana regeneration, using two of them at the same time doubles that again. This enabled the possibility of using 4 Shamans to fully top everyone’s mana pool every 3 minutes (4 Mana Tide Totems provide you with 51200 mana on a 50000 mana pool at level 60) – which is hilariously broken of course.