Agree it's very expensive at level 11 and would have to be used almost as an emergency. By Tier IV though you would be able to get at least 1 off per short rest and still have plenty left in the tank for other things. I actually thought they might be too powerful even at the high di cost.
Eh, Storm of Blows is only really powerful if you have more than four enemies around you. The max damage seems strong, but in reality you aren't truly increasing the damage, just guaranteeing an unlikely result. Essentially, if you are looking at 4 enemies, is 5 ki worth increasing your average damage by 4 points? And spreading that damage out instead of being able to focus fire it? No. I don't really see a time when I would use this unless I was surrounded by like 8 creatures. And even then, I'm more likely to spend 1 ki disengaging and running than I am 6 ki to make a single attack against all of them.
Dance of the Wind.... Four Elements taught us that, generally, spending ki = spell level is not quite worth it. Step of the Wind is an hour long non-concentration spell, and at 4 ki it would be considered too expensive generally. You are charging 8 ki, double that amount, and getting one-sixtieth of the duration. The free use of Step of the Wind seems nice, but it becomes a question, are you going to use step of the wind more than four times in the next minute? Because if you aren't, then you overpayed for this.
Aggressive Defense... this one is tricky. Turning a hit into a miss? That's good. Moving and attacking is good too. But... it isn't always useful. For example, let us assume there is an archer attacking you, and all the archer's melee friends go next in the initiative. Then even if you are hit, you aren't going to want to spend this, because you will simply be serving yourself up on a platter for the enemy. Considering how risky moving towards the enemy might be, and the unlikeliness of two attacks finishing the enemy... I might go for 3 or 4 ki, to react and turn a hit into a miss, then move and attack. Which seems cheap, I know, but 4 ki is 1/6 of the maximum ki a monk can have, and this is only situationally useful, even if it can be powerful