Hello,
Arena is about making clever teams. No single team nor ninja is unbeatable in arena, not even Fusion Kisame. If you are having trouble with him you may need to try a different combination of ninjas. That said, Kisame is a very expensive ninja. He costs quite a bit just to get to four stars, and many people are reporting hundreds or a thousand vials just to get his skill breaks. That seems an ample cost for a powerful skill break. Those people would disagree with nerfing him after paying so much to finish his skill breaks.

As for SSP Naruto, can you clarify what about his kunai you have an issue with?

Thanks!

For fateful choice, It isn't easy getting the stuff to get him

I understand now what you meant about the 146 flying raijin kunai. That price for Naruto SSP in the Fateful Choice event, while it seems high, is actually not that high, all things considered. Keep in mind that resource prices in events are largely arbitrary. That could be 146,000 kunai if the amount of kunai given out are increased 1000x. What matters is the actual coupon cost. According to the accepted breakdown cost, Naruto's price this week is around 12k to 17k, so an average of about 15k. Considering that he debuted at 25-35k, that's a pretty fantastic deal for such a strong ninja! And this isn't even the cheapest price he gets down to! If you aren't happy with this price, then you could wait for when he's in Time Limited Ninja Recruitment (he was there for about 12k average last time it happened).