Continued from this thread.
To respond:
Nice catch Kinevon, its key that the pool needs to be on the ground.
That said, I don't think the whole party will be constantly on air at these levels. Flying might be easy to access, but for small amount of time.
Also the radius IS pretty big. 5 foot per age category makes it 50-60 feet radius. The ability doesn't specify a range. If the dragon can target it within the reach of his breath weapon then its very hard to avoid for the party.
Casting antimagic field on a dragon is very hard to counter, I would never do it as a dm. It is also a well known issue though, even before Oots:P.
To recap a CR 16 creature can deal 40d6(140) acid damage in a 50-60 radius area with reflex save 28 for half, the damage unlike the red dragons melt stone scales with the breath weapon.
Personally I think its a tad too stong and I would change it to work like melt stone: Full damage on the first round, immediatly halved after the first instance of damage.