yes sotb stacks with other mana regen buffs, and the reason there's nothing in the list for lvl 36 is because the only spell we get at 36 is equinox which is a grp rez and non-upgradeable. Get sotb and spores is my advice.. prolly frostbite for last one but you wont' be able to use that til 39 so dunno how much that'll matter to you.