I would love to hear a rioter respond to this, I'm legitimately curious. For example, Katarina doesn't use mana. So, in exchange for that luxury, what does she lose in exchange? Mobility? CC? Not only just her of course, I'm talking in general, what were the ideas to compensate for manaless champions? And if it was specific for each champion, please give me a thorough explanation as to what that specific thing was.
TheSlogs1 votesWell I can tell you that in order for 
to function properly as a champion she has to have no mana requirement. Her passive would need to restore mana as well, which personally I don't think to many people would mind. being limited to mana would make half the community happy, and half of it not.
Sassmast3r1 votesWell yes, I do agree, it would completely change her kit. However, I was curious, what is she LOSING by not having to worry about recalling from having no mana? Is she actually losing anything?
TheSlogs1 votesRange is the only thing I can think of. Most if not all mana-less champions are melee. 
is the exception because he is different, and even he can be considered more of a melee person.
Hoffmisc1 votesChampions without mana are meant to limited by their cooldowns, but seeing as how all of Kat's abilities already have low cooldowns this is effectively nonexistent to Kat.
hadre1 votesnot really... when they design a champion they what the champs abilities are then determine if a resource fits. Kat would be the worst champ ever with mana. Give her standard mana costs and she litterally couldnt farm passed level 3 because her abilities do no damage and shes melee. Then to get her in middle of combat and not necissarly have the other 250 mana a normal full rotation spell at 6 would cost would just break her.
hadre1 votesit changes on champion 
has long CDs 
has low base stats 
has terrible scaling. gives up CC. 
gives up his mobility (all he has is his passive around brushes)
Sassmast3r1 votesCan't Rengar jump? And thank you for providing an explanation, now I partially see how the compensation has been made :)