When I pop into ToL, it's usually mid fight when healing is most intense. By this time I'm usually at half mana ( this is in normal cata dungeons, not heroics ). So I pop the cd...now, stacking LB like crazy is the best option obviously since LB is pretty much the only good spell resto druids have right now. But what's the point of making regrowth instant cast? Usually at this point 2 or 3 casts of it and I'm OOM so I don't even touch it unless the tank is at 10k health or something.
So why not chage ToL to also reduce the mana cost to spells slightly. I'm not talking by 2k or something. But even knocking off 500 mana from each heal would help come those last few seconds of a boss fight when a resto druid is probably OOM and the only thing you can do is pray to the WoW gods.
This isn't about QQ. This is about a small change that makes ToL a better option and make more sense.