Treasure Chest have been changed (as other cards of this set).
Pirate Island could be very useful to protect your permanents (but you won't be able to use them while protected this way) or to deny permanent use to the opponent for one turn, because when they unburrow they lose the turn and they have to wait for the next turn to be activated.
The problem of the pillars is resolved because when you burrow a pillar it goes out of the stack, so you can't burrow all the pillars at one time this way.