Main char mystery is generally stronger than regular ninja counter parts.
Sakura have pretty much the same mystery as water main, except it heals more, thus to be consistent with above, the jutsu needs other perk, in this case 0 cost is the perk.
As for dance, you need to try and build an effective dance team in order to see its limitations. It's used for mutli/chain casting. For any other purpose, rasengan works just fine. And chakra management is very important for multi/chain casting, a chakra cost would be heavily detrimental. If you pay attention, you will see that almost every single wind team that uses dance have chakra generators, there is a reason for that. In any case, wind is currently one of the least used class, so it's probably on the weak side, there is no reason to nerf *ready disadvantaged class*. If there is ever a day for wind to be the OP class and need nerfing due to this skill, increasing cd might be the better option (or perhaps make debuff removal only remove 1-2 stack)
about wind being underused* according to S2-S12 LA space time battle point ranking there are:
0 wind in top 10
1 wind in top 30 (rank 20)
3 wind in top 50 (rank 20, 42, 48)
9 wind in top 100 (rank 20, 42, 48, 56, 78, 85, 89, 93, 94)
Note that I did not directly say this prove wind is weak, just that it is under used. Space time is by no mean a good indicator of PvP prowess, however it does roughly go in the order of power and this shows that of the top powered player, few player uses wind. This INFERS that wind is weak, does not prove it.
On a side note, water is slightly under represented in to 10 and 30, but becomes on par afterwards.