The way we see it, Intellect increases the power of your heals. Spirit (and other regeneration mechanics) replenishes your mana. Having Intellect also increase the size of your mana pool complicates things. It's harder to balance, and feels worse for players trying to balance their character.
While we think the healer mana model for Cataclysm is sound and ultimately accomplished what we wanted, it was still a little too difficult for a on fresh level 85 just going into dungeons, and a little too easy for raiders. Part of that comes from what improved stats do for healers: they get bigger heals (from Intellect), the ability to cast more heals (larger mana pool), and the ability to cast those heals for a longer period of time without running out of mana (as a result of regen). Along the way, the tank and the group are take more damage from tougher bosses, but also have higher damage and higher survivability from improvements to their own gear.
Please remember, the goal isn’t to make healers so resource-starved that they can’t heal. That isn’t fun. The goal is to reward healers who limit how much overhealing they do (in other words, play smarter) for their efforts. You limit your overhealing by doing things like casting a smaller heal when a smaller heal is sufficient, or casting a slower heal when death isn’t imminent, or casting a single-target heal when the group isn’t all taking damage at once. Skillful healers should prosper. When players feel like increasing their skill doesn’t increase their success, they tend to get bored or frustrated.
I wish I could agree with the CM on this one but I can't. Right now I don't heal I went Ret and only heal as a sub. I healed for 3 years and stopped because it was no longer fun for me. While I don't like a lot of what Ghostcrawler and his team have done since he joined Blizzard that is what they are paid to do. Healing is one of the most stressful roles that any player can take on and time and time again I see Ghostcrawler and his team make it even harder for healers. I blame Ghostcrawler he is at the top. Healing should be fun. Healers should feel like they are powering up as they get gear it is one of the reasons to raid. Players don't want to be balanced they want to feel powerful. You take that out of the equation and there is now reason to progress your character.
Sadly as time goes on I see a really lack of new ideas in WoW. I not even sure if I will contiune playing in MoP. I've seen Star Wars and I must say the fun factor is there in game. SOmething I haven't had in WoW since BC. Bioware has added some amazing things to their MMO changes that make the game fun and engaging.
Blizzard on the other had has really done nothing to really change WoW for the better. Still have the same graphic models they had in vanilla. Still have quest givers and NPC you could care less about just click on them and click accept. Endless grind that feels like endless grind. If you are going to make us grind at least make it fun.
The point is why change what isn't broken how about working on things to the game fun again.