The results of the analysis are shown on google docs here:
Link to Results - Google Docs
The tricky thing with Flameglow is that it doesn't scale very well, so it will probably have to be re-adjusted every patch just to stay up to par. The spreadsheet shows the results based on sims of the 'average' benefit, because you will not always receive the same benefit every time - due to the damage reduction being based on how hard you get attacked for.
If the change that I suggest is implemented, it means that - on average - Flameglow will be equal to Ice Barrier in non-upgraded S13 Tyrannical 493's when you gear is gemmed and enchanted ( a typical scenario ).
In case you do not want to view the summary of results spreadsheet, I have included the recommendation below:
The current tooltip...
...in my opinion, should be...Flameglow
Protects you with fiery energy, absorbing [ 20% of Fire Spell Power ] damage from each attack against you (up to a maximum of 30% of the attack).
According to my info, this is the optimum setup for Patch 5.2. It strikes the fairest balance between "DoT-type attacks" (by this I mean things like DoTs, fast auto-attacks, pet attacks, etc.) and other attacks. It is important to remember than this is based on average - when you are getting attacked by someone using major cooldowns, the harder your enemy hits you, the worse Flameglow gets devalued. (see Post #14). The spreadsheet is now corrected (thanks to yurano for your help) with error-free information.Flameglow (re-evaluating)
Protects you with fiery energy, absorbing [ 40% of Fire Spell Power ] damage from each attack against you (up to a maximum of 20.6% of the attack).
Currently, Flameglow is actually overtuned. It provides a DoT-type passive damage reduction (on average) equal to ~27% during regular-pressure scenarios and (on average) reduces burst scenarios by ~4.5%.
With the change I suggest, it transfers a portion of that currently-overtuned passive damage to reducing slightly more burst. It equates to approximately the same damage reduction as current (~15%) - just with the power shifted a little to provide a *little more* defense against burst, and reducing the overtuned damage versus the majority of some classes' attacks (this way, classes who rely on lots of small attacks are not as negatively affected as much as they are currently). This change puts FG at about the same EH level as IB in S13 493 gear, whereas currently it is over the EH level of IB.
With the change, Flameglow would provide a DoT-type passive damage reduction (on average) equal to ~20% during regular-pressure scenarios and (on average) reduces burst scenarios by ~10%.