How badly did they gut Mana Regen, you ask?
"Doran's Ring gives 3 MP/5 plus another 4 MP/5 if you last hit every minion (4 per minion, 6 minions every 30 seconds). So two Doran's Rings is ideally 14 MP/5, simple enough.
The amount of mana that Chalice (or Athene's, which gives the exact same amount of mana regen now unless you get a kill or assist) gives you is +50% base regen and +2% missing mana as MP/5.
The champs with the most mana regen are actually ADCs (and Leona and Nautilus) ironically, but once you get to mages, there's a pseudo-standard of 6 MP/5 at level 1 and a growth of 0.8 per level. For mana, there's some slight variation, but the most common value is 334 mana at level 1 with a growth of 50 per level. (There are some mages that get a fair bit more like Cass, Morg, Karthus, Janna, Soraka, Zilean, and Kassadin, but it's like an extra 10 per level with 20-30 more at level 1.)
So we need to figure out at what point the MP/5 from Chalice is greater than 14. Let's assume champs are operating around 50% mana most of the time. That means that Mana Font is giving around 5.8 MP/5 at level 6 and around 7.3 at level 9. The +50% base regen will be giving 5 MP/5 at level 6 and 6.2 at level 9. Chalice is basically breaking even with Doran's around level 9, maybe closer to 7 or 8 if you operate at significantly lower amounts of mana. You do have to consider that while you were working your mana count down that low, Doran's would have been giving you back more, though.
So you can see that double Doran's actually gives more MP/5 potentially even as late as level 9 if you last hit perfectly. It also costs 200 gold less than Chalice, gives 30 AP, and trades 25 MR for 120 HP (a slight loss in defenses against magic damage for the early game, but you can spend some of that money on potions).
If you don't actually want magic resist, there is now basically no reason to ever touch Chalice. Chalice is not an efficient mana item. Get double Doran's and build your core. If that core wants CDR, go Morello and use Idol + Doran's Ring as your use of 1000 gold rather than Chalice if you're worried about mana."
~ the_rowan http://www.gamefaqs.com/boards/954437-league-of-legends/71053866/809420219
Note also that the MR is less beneficial than flat HP when laning against champions like Zed. (So basically every game.)
Another important note is that Doran's ring still gives a flat 3mp/5. It was not buffed to Athene's/Chalice's level - they were just brought down to being about as useful(less) at sustaining mana as two Doran's used to be.
So, who was saying that mana regen was buffed across the board? Something about Zed being meaningfully gated by energy?
