User blog comment:Emptylord/Sandbox/Custom Patch Notes/@comment-1330314-20140324195326/@comment-1330314-20140325043320

I actually badly worded my own initial point: if the percent mana regen of every champion gets tuned so that they get the same initial mana regen as they have now (i.e. Ashe gets good regen and Taric gets crappy mana regen), mana regen items would work a lot better on champions with high mana rather than low mana, negating the restriction imposed by their base mana regeneration. Ashe may not be the best of examples, as she doesn't usually build mana or mana regen, but champions like, who have large mana pools but weak mana regen, would very quickly not be bounded by mana restrictions at all.

The problem I see with "effective regeneration time" is that this goes against the goal of mana as a gate to ability use. Abilities have fixed mana costs, so with flat mana regen you can ensure you have enough mana to cast a certain ability within X seconds. If you run out of mana, that means you need to return to base. Not even mana regeneration is supposed to guarantee you permanent lane presence. Mana, mana regen and ability costs are all balanced around each other, and flat mana/regeneration simply adds to that. Percentage regen means champions with a large mana pool, who can already spam a lot of abilities in one burst without running out of mana, also get to throw down a lot of abilities over time, whereas champions with the same regen but a small mana pool will have both worse burst potential and higher costs to ability usage over time.