Lifebound Alchemist Stone

[Ethesae]

Howdy folks. I've been looking for answers on this, and seeing as how its +5 points I'll probably make one anyway with the abundance of volatile lives you get from herbing anyways, but I did a quick analysis on this trinket for healing and figured I'd share.

First off the trinket:
Lifebound Alchemist Stone
Binds when picked up
Unique
Trinket
+380 Stamina
Blue Socket
Socket Bonus: +10 Critical Strike Rating
Requires Level 80
Requires Alchemy (500)
Item Level 359
Equip: Increases your mastery rating by 213.
Equip: Increases the effect that healing and mana potions have on the wearer by 40%. This effect does not stack.

Essentially the mana gain from potions can be thought of as spirit that is proportional to the fight length. I just did a quick calculation by fight length in minutes. The equation is:

d(mp5) = d(spirit) * sqrt(intellect) * 0.003345 * 5

Where d(mp5) is 10000 * 0.4 / (Fight Length (seconds) / 5)
I assumed a value of 3100 intellect. This is what I had when I hit 85, but if you have more these values will be lowered.

Fight Length (Minutes) - Spirit Value
1 - 357.9578
2 - 178.9789
3 - 119.3193
4 - 89.4894
5 - 71.5916
6 - 59.6596
7 - 51.1368
8 - 44.7447
9 - 39.7731
10 - 65.7958

It seems to me the common value probably lies around 90-70 spirit, though for heroics this is obviously better than raids due to the shorter fight length. I'm also assuming you're chugging those fancy new 10k mana potions. Using those 22k dreamstate potions would obviously increase this by over double, and there's also the blue socket to consider giving another +40 possible spirit.

So, is it worth using? And if so to what point? I should also note that I'm not raiding yet as my guild raids Tuesday/Sunday, so I'm not totally sure as to the average fight length there.