I used to only see this once in a while, but it is getting more common. It's getting to the point where it appears to be an all star more often than not - because by the time you can get to them, they've done significant damage. If you are also defending the first waves of attacks, you'll never defeat the damage or recover from the exploit.
On the upside, there's always another match. At the same time, it's frustrating to have a team line up defenses, use consumables, have cacti & choppers set up perimeters with their timed abilities and man the pots...
Just to have someone who found a kewl exploit yoink the fun of the attack and defense away from everyone else.
Patch this soon, please.