@kupo:
Shields are nerfed to a point where you would want to use spotdodging as an alternative defensive mechanism with the addition of shieldstun, so I think that they are fine where they are now.
If people are encouraged to use spotdodges instead of shielding then that's fine by me, but I see no reason to nerf the spotdodge or the airdodge from where they are now. Yes, they are good. No, they are not broken. The spotdodge has the same duration every time. Just learn to time your attack so that it hits them as they come out of the lag (assuming they didn't spotdodge a super laggy move of your own, in which case, where's the problem here?). The airdodge has a predictable trajectory. It's certainly punishable.
Now, for stopping people from airdodging while in in a tumble... Let me just say that stopping airdodge while in a tumble will do nothing to nerf the defensive game. Do you hear me? It will do nothing. All your opponent needs to do is tap left or right on the control stick when they go into the tumble, and they will be set into their freefall position, allowing them to airdodge again. This existed in melee, too, although people didn't usually airdodge out of it since they were often too high in the air for the airdodge to be effective.