Holy Tree: When to switch from spell crit to MP5

[JohnnieRat]

So I was reading on the forums today someone trying to theorycraft whether or not we need to switch from Spell Crit to MP/5 as a result of the illumination nerf. His argument had many holes in it so I'm trying to put something together. I am assuming that as a full Holy Pally, your tree looks something in the vicinity of http://www.wowhead.com/?talent=sVxhbgzheox ... put the other talent points where you want as this is sort of baseline.

Assumptions:
-1% spell crit (increasing it would make a linear growth so I'm starting there)
      -> FoL would have 6% crit rate (based on talents)
      -> Holy Light would have 12% crit rate (based on talents)
-You are chaincasting only 1 of the healing spells constantly without stopping (I know that's not how things work but bear with me)
-Max rank FoL = 180 mana
-Max rank Holy Light = 840 mana
-1 minute fight (easy number to work with)
-Imp BoW gives a base of 49.5 mp/5

Number Crunching: (I'm only using Flash of Light... because spamming Holy Light = OOM very fast)
       FoL
60 seconds/1.5 second cast = 40 casts
40 casts/6% crit = 2.4 crits => 432 mana (pre-patch) so you get 259 mana (at 60% Illum returns post-patch) = 173 mana difference per 1% spell crit per minute
40 casts x 180 mana per cast = 7200 mana used
60 seconds/5 (for mp/5 sakes) = 12 "ticks" of mana return
12 ticks x 49.5 base mp/5 = 594 mana from BoW in a minute
173 mana (difference between 100% and 60% mana return per 1% crit in a minute) / 5 (mp/5) = 34.6 mp/5 per 1% of spell crit that we have (what it will take if you want to get back to the same healing power as we had before the nerf.)

In conclusion: it is going to take a massive amount of mp/5 to make up for the 40% loss in Illumination so stacking spell crit is still probably your best bet in maintaining mana efficiency. Personally, I'm just going to go for a huge mana pool and balance out spell crit and mp/5 just using my best judgement based on the other stats on the armor. MP/5 has always been more reliable than spell crit and works out for longer fights anyways because crits have this tendency to strong together and than not happen for a while. And level 70 Holy Pallies have around 15% spell crit before talents anyways... so the mp/5 needed to compensate is unnattainable.

Please critique this and improve on it if you can (I know y'all are smarter than me too so the list of improves should be long  )

Disclaimer: I am a Political Science major and Infantryman so my math skills are rather sub-par. My biggest math feat is: if my platoon has 45 people, and each person needs 200 rounds of ammo than we will get half of what we need from supply.

[voctovian]

Well, I dont think pallies will ever heal as well as pre-nerf, but here is the way I choose to itemize gear for MP5 and Spell Crit.  Ultimately, it would be best to have high mp5 and +spellcrit, but there are always compromizes...

Raid Scenario
In a 3 minute boss fight, assuming approximately 185mp5 (including Blessing of Wisdom), the highest total mana I can use is

10500 (Base mana) + 36 * 185 (from MP5) + 4800 (2 x [wowitem]super mana potion[/wowitem]
= 22k mana

If I add gear that increases my MP5, each point increases my mana recovered by 36.  If I add 1% spell crit, I recover 22k * 1% * 0.6 = 132 mana

Thus 1% spell crit = 3.6mp5.  Alternatively, since 1% crit = 22.1 +spellcrit

6 spellcrit = 1 mp5

Non Raid Encounter

Now suppose we go with a 80sec encounter, and no pots are used

Total mana used = 10500 + 16 * 185 = 13400

1mp5 = 16 mana, 1% spell crit = 81

So, 1% spell crit = 5 mp5 or 1MP5 = 4.4 +spellcrit

Using these numbers for gear selection

These numbers are useful to gauge, for example, what gems to use... for uncommon gems, you can choose either 2mp5 or 6 +spellcrit.  Clearly, for mana efficiency, the MP5 gem is better

Caveats

This does NOT take into account the additional healing that a crit heal gives.  I need to do further investigation to see what gives the most healing, as that is what is most important.  However for some encounters, crit heals are needed to keep the target alive, mana efficiency is secondary.. Rokmar the Crackler (Slave Pens Heroic) is an example of this.  Without 3k healing per second, it is tough to remove the Grievous Wound (bleed) debuff. 

[Arcdelad]

good use of the word caveat