Usukane aren't Tsukikazu. I can't help but wonder if you're supposed to know that, considering you wrote a "guide" on this event.
For the record, Tsukikazu are exactly the same as Ubuginu, Tatenashi and Hachiryu, so why you've singled out one Armor when your guide covers all four of them confuses me.
In any case, yes, it seems Usukane is simply put into this event to make it tougher. On Phoenix what must have been at least eighty players threw themselves at this thing in South Gustaberg, and much slaughter ensued:
The last 10% of Usukane's HP. (150k)
Note the repeated deaths of some people - They simply had their Home Point set to Bastok Markets and rejoined the fray ASAP.
In the end? She dropped 4 Gold Carp to the player that got the last hit in. Which are next to worthless and certainly not worth 25 minutes of 80+ people's time.
So basically, they're meant to be avoided. Nothing else.