Some mana math that will calm you down (I hope)

Let's take an example (Anivia) and look at some numbers.

Anivia's current base mana at level 18: 396+50x17 = 1246 Pbe: 495+25x17 = 920

920/1246 = 0,738... So she will have about 26% less base mana.

Anivia's current mana regen: 1,2 per sec Pbe: 1,6 per sec

1-1,2/1,6 = 0,25 Mana regen will be 25% better. 60x0,4 = 24 extra mana per minute.

Theorically this means you have about the same mana available as before. When gaining 25 less mana from level-ups, you probably have restored the same amount back already. In my opinion the changes are only worse in the late game scenarios where you need to cast a lot of spells and don't have time to regain mana anymore. For laning phase however, not so bad. Remember that your mana pool is increased for the first few levels. And as you know, it's mostly the early parts of a match that decides how the rest goes, so I wouldn't be expecting these mana changes to dramatically making mages less viable or harder to play.

Am I right or are there huge holes in my calculations and thoughts?