Such as 
because 
and 
(in 's case) were necessary for these champs to just be able to poke / farm during laning phase and not instantly become oom.
And let's not forget the champs with the most mana issues in the early - mid game:
and 
Silent Pace1 votes[deleted]
JavelinJoe1 votesTear's "buff" changes the mana regen to only gives mana back (apart from the current mana passive stacking to 750 additional mana) if you spend mana, and only 25% of what was spent. So IMO it is a nerf. My issue with Athene's is that unless you have a shield or a heal (not self mind you) the item is worthless just like Ardent Censer is because the stats it gives are too small (40 AP, 20% CDR, 25 MR, and 75% mana regen isn't really worth 2100 gold and a full item slot since all the stats would cost you 1975 gold if purchased individually with 
850 gold 
450 gold 
125 gold 125 gold 125 gold , 20% CDR is roughly a 300 gold value at minimum).