First and foremost, there are no calculations or data shown in the spreadsheet. In particular, there is no justification as to why Flameglow is attributed a flat 90K EH. Specifically, what test/classes/data was used to determine the 90K EH? Moreover, there's no justification as to why Flameglow EH is assumed (falsely) to not scale with Resilience. In fact, Flameglow scales better with resilience than Ice Barrier. The effective health of Flameglow's SP absorb scales equivalently to the effective health of Ice Barrier's absorption with respect to resilience. However, as resilience increases, the Flameglow 30% cap improves (in terms of EH), increasing the percent absorption of larger hits up to a maximum of 30%. In other words, as hits become weaker, Flameglow is able to
30% max absorb a greater portion of incoming hits. Due to this 30% cap, Flameglow scales better with resilience than Ice Barrier, albeit marginally.
Put simply, Ice Barrier is worth 4580+SP*3.3, or 78830 with full Tyrannical, shielding after resilience. The work lies in determining the efficacy of Flameglow in different situations.
The OP asserts that Flameglow is garbage in all situations. The following analysis shows that there are several situations where Flameglow is effective, primarily against DPS with frequent small hits (dual wield, DoTs, etc).
In the following analysis, I have used full Tyrannical characters on 5.2 PTR. A Subtlety Rogue and Shadow Priest will bash on a Flameglow Mage from 100% health to 0% health during a duel in two modes: Standard DPS and Burst DPS.
Their character stats are shown in this image.
Rogue - Standard DPS - Garrote > Backstab to 5CP > Evis > MfD > Evis > Backstab to 5CP > Evis > Mage Death. Here I've chosen MfD to maximize burst, exploiting the weakness of Flameglow. We see that in the ~18 sec to kill the Mage, Flameglow absorbed roughly 110K, significantly more than Ice Barrier. Moreover, due to the 7 sec advantage of Flameglow due to Ice Barrier's 25s CD, Flameglow could continue to absorb more damage with heals. This is highly possible in team play (eg. arena).
Rogue - Burst DPS - Garrote > Shadow Dance > Ambush to 5CP > Evis > MfD > Evis > Ambush to 5CP > MfD > Mage Death. We see in the ~11 sec to kill the Mage, Flameglow absorbed ~50K. This encounter shows the weakness of Flameglow to burst damage, especially multiple 80K Ambush Crits and 40-45K Evis/Backstab hits. Without incoming heals, Flameglow is weaker than Ice Barrier a burst scenario, but Flameglow isn't completely useless.
Shadow Priest - Standard DPS - 0 Orb > Mind Blast > Dots up > 3 Orb DP > Mind Flay Insanity > Execute > Mage Death. We see that in the ~27 sec to kill the Mage, Flameglow absorbed roughly 125K damage. Again, Flameglow out absorbs Ice Barrier by a large margin.
Shadow Priest - Burst DPS - Start w/ 3 Orbs > Dots up > 3 Orb DP > Mind Flay Insanity > Execute > Mage Death. We see that in the ~13 sec to kill the Mage (3s lost to putting up VT/SWP), Flameglow absorbed roughly 110K damage. We see that in a DoT based burst scenario like DP + MFI, Flameglow is able to hold out quite well.
All in all, we see that Flameglow can be competitive with Ice Barrier in situations with a large number of small hits. In these situations, Flameglow is able to absorb a large amount of damage and is
reset/recharged with healing. In contrast, Ice Barrier is a
use once and gone ability. Flameglow in its current iteration is clearly superior to Ice Barrier in small hit scenarios and should hold its own compared to Ice Barrier in medium hit scenarios. Only in large hit (burst) scenarios does Flameglow fall behind. Even in the burst case, healing can cause Flameglow to be a better choice than Ice Barrier. Ice Barrier's efficacy is only guaranteed temporally close to its activation since it can be dispelled or depleted. In contrast, Flameglow is active whenever the Mage is taking damage and is
reset whenever the Mage is fully healed, common in team-based PvP.