gotmilk0112 wrote:People have said that SH only applies to the base heal amount on your heals; is this true?
Yes.
Bah!
I really hate being wrong. But this time I was. Big time. Sorry about that. Spiritual Healing does indeed only affect the base spell. Man, I healed all through vanilla wow convinced that Spiritual Healing affected +healing. Some things you are so sure about that you don't even question it.

gotmilk0112 wrote:This also ties into the whole "2 minute stat weights", how int/max mana are valued much higher than bonus healing for shorter fights, and just about every fight in T1 content (barring ony/rag) is under 3 minutes, so 10% mana would be better than 10% healing in this content.
Thoughts?
On the face of it, one might think that 10% mana from int and base mana vs 10% healing should be roughly the same. That isn't however the case.
Let's start with a priest like me who buffed has roughly
8000 mana
350 spirit
500 +healing
70 MP5
3 set Transcendence.
The amount of mana I would get from the +10% talents is 800. Over a 2 min fight where I spend 90% of the time inside the 5SR, use a Mana Potion, and use a Dark Rune I will generate a total of.
Base+Int: 8000
MP5: 70*120/5 = 1680
Spirit: (6.5+350/8)*120*(0.3+0.7*0.1) = 2231
Manapot: 1800
Dark Rune: 1200
Inner Focus: 556 (Max Rank GHeal, sometimes even PoH)
Summed up: 15467 mana.
Thus, I'm really only getting 800/15467= 5.1% extra mana
So in theory I'd be able to convert the extra 5% mana into 5% more healing, I do however get 7-8% bonus healing from the Spiritual Healing talent and that is frankly more reliable extra healing as well.
A few example spells regarding how much % healing they get given the stats listed:
Flash Heal Rank 5: 6,9%
Flash Heal Rank 7: 7,8%
Heal Rank 2: 4,8%
Greater Heal Rank 1: 6,6%
Greater Heal Rank 4: 7,9%
Prayer of Healing Rank 4: 8,5%
Another approach to take is to try to convert both talents into stats, since you talked about Int being better than +healing in short fights wich is true in the standard case. If we ignore the crit portion of int then 800 mana is about 50 int.
+10% Healing corresponds to roughly this amount of +healing on commonly used spells:
Quick and dirty calculation: (AvgTooltipHeal*.1) / +healingscaling
Flash Heal Rank 1: 50
Flash Heal Rank 2: 67
Flash Heal Rank 3: 84
Flash Heal Rank 4: 103
Flash Heal Rank 5: 132
Flash Heal Rank 6: 164
Flash Heal Rank 7: 207
Lesser Heal Rank 1: 31
Lesser Heal Rank 2: 27
Lesser Heal Rank 3: 27
Heal Rank 1: 44
Heal Rank 2: 54
Heal Rank 3: 71
Heal Rank 4: 88
Greater Heal Rank 1: 112
Greater Heal Rank 2: 142
Greater Heal Rank 3: 178
Greater Heal Rank 4: 222
Greater Heal Rank 5: 243
Prayer of Healing Rank 1: 109
Prayer of Healing Rank 2: 160
Prayer of Healing Rank 3: 237
Prayer of Healing Rank 4: 338
Prayer of Healing Rank 5: 375
This paints the same picture. In the short fights where Int is a lot better than +healing (to a limit where you cannot reasonably use all mana in a good fashion) you will use more of the expensive spells and thus the talent will be worth almost 200 +healing and that blows 50 int out of the water. In longer fights, it will be worth less healing, but, on the other hand, the relative value of Int will go down in those situations too.
Both methods use ballpark figures, but they independently value Mental Strength at about half the value of Spiritual Healing and even less in longer fights. I hope you are satisfied with the answer.