I've read over the last 2 years a few fair evaluations of the mix match versus usu sets. This is as fair a one as I've seen, but still I find all of them wanting for completeness. If you want to say its because I have full usu, I would only say I have the option to wear either and still use full usu due to the following.
These sets are subject to exactly what you have said Failure, in that they can be considered situational. However I have noted that so many of the comparisons seems to give short shrift to the evasion, the stp and to exactly what are the conditions that one would choose either set.
Evasion: From some analyses, not specifically this one, since you have acknowledged the defensive abilites of the full set, the value of evasion is being ignored. My evasion rates are significant in the areas my sam melees. Of course, I am not referring to Kirin or Tiamat, but then again, I am not talking about salvage either. What evasion does is not simply reduce damage taken, but ultimately from time to time, eliminate a death which would cost an empirical amount of lost damage while weakend. I would not presume to know how much that is, but it's not zero. Ignoring this from an overall damage perspective assists the mixed set only. I can imagine (not totally without facts) that I avoid at least 1 death every 3-4 hours when I am on my sam because when I pull hate I get at least 1 extra miss at a fortunate time.
Stp: Have we agreed that the 'extra' stp on the full usu set has no value? Is there no value in being able to have more gear options regarding 6-hit builds using one set over the other? I would only suggest, making that assumption and not quantifying that assists the mixed set only.
I don't really disagree that one of these sets is better under certain circumstances. Perhaps one set is better under every circumstance. I don't think we've done a great job of quantifying those circumstances to a degree where we can say on paper 1% haste or 4 acc or 60 evasion or 6 stp clearly creates a winner.
It's not that I think that all things considered they are too close to call; I just have not seen enough math to say exactly what it is because things (I mentioned above) are not being quantified in the damage calculation.
In my own, less that skilled mathiness, I've drawn a conclusion that making a change is not warranted. But as always, I am eager to be wrong and to improve.
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