Interesting. You may need to provide a little more info in the card itself to keep players from getting confused, but I like the idea...
I am a little worried it might step on sanctuary's toes a little bit, but its definitely quite distinct in its function.
I;m not sure on the balancing for an attack power version of swarm. I worry this may be a little too powerful in conjunction with mitosis or fractal...
Will this card be affected by its own cloak or the cloak of nearby locusts? If so, then I think it will be OP when combo'd with fractal since it would not only grow very high in attack power, but would also provide its own powerful anti-CC. If not, it should be ok.
Also, suppose someone casts, say, plague. What how will this interact with the field invisibility?
In the case of cloak, the cloak was destroyed. I would assume that wouldn't be the case here... If that is so, how will the field invisibility effect be handled?