Comparing maximum mana values at level 18 for mages/supports, some look really... wrong

http://leagueoflegends.wikia.com/wiki/Champion_statistics_at_level_18

Looking at this page, I realized that several of our mage/support Champions have been left with a severe deficiency in how high their maximum mana is, while certain others are either too high or seemingly got rolled a lucky number.

Cases of high amounts:

Janna - 1497.52 Zilean - 1380.8 Soraka - 1370.8

Cases of low amounts:

Lux - 1184 Nami - 1108.24 Sona - 1105.6

Why does this matter at all? Because those Champions who get high maximum mana get more out of Mana Font than those who are medium/low, and they just have more overall to use spells with. Doesn't matter if their spells are costly; they still have a large pool for a Grail/Mikael to work with. The ones with low amounts either have to try to build a mana item for Mana Font to be worth ANYTHING, or just have to live with constant burnouts in late-game, which really makes them a lot less fun to play.

Why am I bringing this up? Because I think some of those mages and supports with low values should get buffs to their level 18 maximum mana. If nothing else, it would keep early-to-mid mana-gating for them, but make them burn out less in late-game.