I was looking at the value of Renew with Borrowed Time, simply to double check the assumption that it's a bad idea, always.
I have seen poor values in the past, based on factors that did not favor Renew, so in testing I'm working with factors that do favor it. Namely: talent points in improved renew, glyph of renew, and more importantly.. with haste values that allow for 6 ticks. I was expecting it to be somewhat better than advertised but nothing to write home about, but the results do seem impressive. The cost however is nothing small. 1905 haste rating, a prime glyph, and 2 talent points that for many would preclude the option of taking Darkness to lower that haste rating requirement. Others will no doubt miss their damage reduction.
This experiment is done via Sim, mind you, and may be in error, although I do try and examine the report for any peculiarities.
In doing this test, I compared 2 gearsets (378 gear), one gearing for haste and the other gearing for mastery.
In haste gear, renew had a HPET of ~35.6k (with pw:shield at 31.6k). In mastery gear, PW:S had a HPET of ~36.5k. crits, DA procs, and glyphs are factored in.
burst healing output with Renew=29k
burst healing output without Renew=27.8k
The profiles went OOM at about the same time, thus sustained healing numbers were also close (with renew slightly ahead).. which would imply that Renewx6 at least made up for the increase in mana consumption caused by the added haste. I cannot factor in everything.. overhealing, which a HoT will likely produce. and I can't easily account for actual healing needed as opposed to healing potential.
Still the question lingers. Is it a viable?
The benefit of taking the SoS/Mastery route would be the increase to PW:S spam, 2 spare talent points, and not needing the glyph.
The benefit of taking SoS with Renew would be more consistent tank healing (faster greater heals, the consistency of a having a HoT up), possibly mana efficiency.. renew is about half the cost of PW:S, and more effective healing output during movement.
Tentatively, the conclusion I draw from this is that at certain gear levels, Renew can be a useful tank heal and that the sacrifices, while not always worth the cost, would greatly benefit movement heavy fights.
profiles I am using are here: (running ~2k spirit each)
W/Renew:
chardev 8 - WoW Cataclysm
Without:
chardev 8 - WoW Cataclysm
I avoided Jaws of Defeat and shard of woe for these, they deserve their own analysis and can definitely change a person's playstyles.. but people can get unlucky on drops anyhow.. and there is certainly not much I can really argue if someone has such things and is using that cost reduction to shield the entire raid.
Also, my apologies that I could not link to the actual report. I do not have a host to upload to. I can however send it if requested.