Diminishing Returns
Can someone knowledgeable explain Diminishing Returns to me? Does it effect Masteries? If I max out things like Deep Wounds, Assassin or Mystic Dispersion am I actually hurting myself as opposed to only putting 3 points into them? I have read all that I can find about it but still don't actually understand how it works. Sorry if this is an ignorant question but I never claimed to be a genius and am confused on what all it will and won't effect.