Effective Health versus Technique

In article after article, and in page after page, guide after guide, and gear list after gear list, the importance of itemization is hawked to us as the ultimate consideration and metric for determination of how "good" a tank is.

But we know it's just not so.

Whether one item or talent or profession gives you 20% more effective health than another item or talent or profession assumes that your character is a complete system independent of additional input.  I get the distinct impression that consideration of the effect of end-game professions for bear tanks assumes that all the other variables are perfect, which we know is far from the case.  What use, for example, is another 1030 health if your healer is running out of mana because you can't keep aggro off of that Fury warrior?  What benefit does additional crit confer if your hit rating is laughably poor?

But I would like to believe that how a person plays their character distinguishes them as "good" as much as, if not more than the cumulative item level of their gear, or the purely numeric effect their gear has on their effective health calculations.  Experience (being the cumulative mistakes I've made) tells me that this is the case.

For example, what is the effective health contribution to a well-timed use of Nature's Grasp or Bash to slow down a fight?

Or, more to the point, what effect does rage augmentation through powershifting confer on us at early levels?  Is it worth the tradeoff between Mangle at level 50 and level 55?  Is the choice to take one over the other purely personal and entirely dependent on play style, or does it actually have an impact on our effective health, and can this impact be measured?

I've made the decision for now to keep five points in Furor, because it gives me an additional weapon to use in a fight, at a time when I am having difficulty keeping my rage bar full.  On paper, it does not confer as much effective health to me as the second tier feral talents, but if I have the rage to keep mobs off of my DPS for a much higher percentage of each encounter, then hopefully it keeps my healer from going OOM as often and in a roundabout way that improves my effective health.

Not through the numbers, but through technique.  And, in my mind, technique is what the game is really about.