Having the Asurans be activated by the player causes a number of problems. You can easily reach the "send a scout to Asuras" mission before even completing the shipyard at Arcanus, and if you do this, you'll be easily wiped off the map with no way to resist. On the other hand if you know this is how they work you can leave them alone until the very end of the GC, only fighting them when you have overwhelming numbers. This makes them a complete non-threat.

Having them active from the beginning and slowly growing or locking away Asuras until a certain number of months have passed would be better.