the spell tool tips are less than worthless saying one thing at point A and a different thing at point B however currently in the game Hex only adds "damage" to spells cast by the Warlock so if a Warlock hexs a enermy then casts a spell which rolls to hit [so not magic missile] then that spell does an extra D6 should it actually
anyone else casting spells at that enermy may find the hex usful if their spell requires a check for example Gale casts Melf's Acid Arrow and hex makes the enermy less chance to make its save for 1/2 damage
honestly Magic Missile is so OP that no other spell is worth doing for single target damage so Hex really isn't good for anyone but the Warlock and pratically always needed for them to keep up with the damage Sorerers or Wizards put out between rests
