After Testing for the last few days, My feedback:
The concept is valid, but the reality does not match that concept.
1. At low levels you actually have enough time between reaching <40% health to take advantage of this ability before you are beyond help. At higher levels the time between reaching <40% and death is near instantaneous the vast majority of the time. If you find yourself at <40%, your primary concern is retreat or healing, not generating more aggro.
2. The scale is not effective. Sure, at low levels before you gain SOs, or even DOs, you can make good use of a +500% damage boost. But the low levels weren't where blasters needed help. At higher levels, bonuses over approximately +200% will be completely lost due to the cap. Therefore the current numbers, while impressive on paper, cannot be realized.
3. The Defiance Meter, as it currently stands, is not helpful. Sure you can place your mouse over the bar, wait 5 seconds, and see what your current "defiance level" is. But in a situation where you actually have anything to look before dying last half a second. No one has time to "figure out" the bar.
My suggestion:
Do away with the Defiance bar. Make the damage bonus scale in direct proportion to the current Health level.
IE:
100% Health = 0% Bonus
99% Health = +1% Bonus
98% Health = +2% Bonus
...etc
50% Health = +50% Bonus
...etc
10% Health = +90% Bonus
...etc
1% Health = +99% Bonus
This will prevent low level blasters from abusing the power, gaining 500% damage solo by falling from a high place to get to 1 Health, and blasting purples with an AE.
This will also allow high level blasters to actually make reasonable use from this ability without becoming over-powering. Typically, a higher-level blaster will only get to 70% Health before panic sets in, and they have to decide to heal or retreat. This produces a bonus of 0% to +30%. This may not be the astronomical numbers of the current scale, but it is something useable more often.
In exchange for the over-inflated damage bonus numbers of the current scale, please consider a small boost to accuracy at various points. I suggest it scale somewhere along the lines of the damage boost. Why? Because if you are having your behind served to you on a platter, it will often be accompanied by "MISS MISS MISS MISS". There is no point in having all that extra damage if it isn't hitting anything.
Thank you for your time and attention.
~Yeshael