Yes, I agree that having high mana regeneration will allow you to use inefficient spells more often. I was reacting against some of the player saying they would just stack Spirit and nothing else because Spirit also allows you to cast big heals or fast heals more often. A hasted Flash of Light is still going to be pretty good in many situations, as is a Flash of Light that crits for a big amount. The numbers should be such that all stats are valuable, not that the guides say “Stack Spirit and all other stats are garbage.” (Source)

[...] We don’t want that either, and in the absence of a five second rule, it won’t help you that much anyway. Instead, we want you to choose whether you use your GCD on a moderate heal, a huge heal or a fast heal. Today almost every GCD is spent on the fast heal because someone will die if you don’t do that and your mana regeneration supports that play style.

Now, we might slow combat down a little to the point at which you have enough time to make a decision about which heal to cast, but that can probably be on the order of 0.5 to 1.0 sec and not 2-5 sec. (Source)