I observed something quite interesting. The renew glyph always removes just 1 tick and boosts the remainder by the same amount regardless of haste.
For those who dont understand what this means
At 4 ticks Glyphed = unglyphed
At 5 ticks glyphed = 4*33 = 132%, while unglyphed = 125% i.e. glyphed heals for 5.6% more
At 6 ticks glyphed = 5*33 = 165% while unglyphed = 150% i.e. glyphed heals for 10% more
For me with 9.42% haste PWS (25.83% haste) nets me one extra tick, while PWS+PI (51% haste) gives two extra ticks.
The reason why this is so intersting is this. Renew does not consume borrowed time, so basically you can cast PWS and 4 hasted renews if you have even a little bit of haste. If you have 10% base haste you can cast 5 hasted renews per borrowed time.
What does this mean
In inner will for me renew heals for 5253 or 6987 if glyphed. Total values including crit and aegis are 5253*4*1.1821 = 24 838 and glyphed heals for the same amount.
With borrowed time however glyphed renew heals for 33037 ,while unglyphed renew heals for 31048
In inner will renew costs 3535 mana and with my values GCD is 1.371 or 1.167 with borrowed time.
If I cast PWS + 4 renews with the glyph the total cast time will be 1.371+4*1.167 = 6.039 seconds and total healing will be 49213 + 4*33037 = 181 361. Total mana cost is 3535*4+9600*0.85 = 22300. HPM: 8.133
flash heal under these conditions heals for 33284 without crit and aegis and costs 9600 mana.
Casting 1 PWS and 4 flash heals on 4 targets (assuming they don't have grace, which you can expect for non tanks), heals for 49213 + 4*33284*1.1820 = 206580 in inner will or 217529 in inner fire. Cast time = 1.371*4+1.167 = 6.651 sec Total mana cost is 46560 in inner will and 48000 in inner fire.
HPCT of PWS+4xrenew inner will = 30 032 for 22300 mana
HPCT of PWS+4xflash inner will = 31 060 for 46560 mana
HPCT of PWS+4xflash inner fire = 32 706 for 48000 mana
If you are under PI, then things get even worse, since you can now fit 5 renews in a single borrowed time and renew will tick 5 times. So HPCT = 255 694.25/6.142 = 41 630.5 for 17840 mana
For PWS+5flash HPCT is
Inner will: 245921.44/6.712 = 36639 for 37248 mana
Inner fire: 36639*1.053 = 38581 for 38400 mana.
For those of you who might be wondering, spells that have a base cast time consume borrowed time even if they are made instant through talents and glyphs. They also don't benefit from inner will (e.g. glyphed holy fire and FDCL flash)
In order for this analysis to be complete we also need to look at PoH.
13593+5290 (aegis) = 18883 with aegis
I am calculating total healing with PoH including crit and aegis by determining the crit boost with 60% aegis and then adding 30% aegis for all non crits:
13593*(1+0.0877+(0.9*0.0877+0.3)*1.2974) = 21468 per target
PWS + 3 PoH = 371 233 healing (5 targets inner will) or 390 908 (5 targets inner fire). Total cast time: 1.5/1.0942+2*2.5/1.0942+2.5/1.2583 = 7.927 sec 46 831 49 314
HPCT PWS+3PoH (5 targets inner will) = 46831 for 32160 mana
HPCT PWS+3PoH (5 targets inner fire) = 49314 for 33600 mana
Incidentally HPM with inner will is 11.54 while with inner fire it is 11.63. So it takes 3 PoH casts per PWS to break even mana wise, if we ignore overheal. PoH is ofc an expensive spell. For cheaper (the cheaper the better) spells you need more casts to break even. However when factoring in overheal, which pretty much eats a sizeable chunk of the HPS benefit from inner fire, Inner will is pretty much certain to be better HPM.
To show that its worth casting PWS straight PoH spam is 46981 HPS in inner will or 49471 HPS in inner fire. Compare that with the values for PWS+3PoH they are practically the same as with PWS+3PoH. Ofc with PWS+2PoH you need to be in inner will, so you lose like 5% HPS. HPM for PoH alone is 14.94 (inner fire).Once overheal is accounted for however PWS has no overheal under heavy raid damage you end up with higher HPS and massively better HPM. With one rapture proc per 2 PWS you are up to 13HPM already in inner will. So very little overheal (15%) is needed to make PWS+3PoH better HPM. PWS + 5PoH might seem like it would be the most HPM, but it will most likely not be. The reason is that its not guaranteed that PWS will be absobed immediately and just 1 PWS per 12s is likely to lose a lot of rapture procs.
The HPM for PWS+4renew for comparison is 8.133.
This analysis explains why using PWS/renew/pom/holy fire and penance and ignoring SpS and heal is so effective. Its significantly higher HPM than SpS and significantly higher HPS than heal, even if you have FDCL or not. Once you get past the 1st haste break point for renew, BT renew will heal for as much as a flash heal for roughly 1/3rd the mana! For stationary deficits on 4 targets this BT renew in inner will is currently the most efficient strategy, especially if you have enough haste to get 5 ticks with borrowed time.
Inner will is better HPM and a noticeably reduced mana drain per second compared with inner fire unless you are spamming SpS without divine insight. This is especially true if you have FDCL
EDIT: Recalculated for 30% aegis.