Great scientists take necessary precautions to you know don't blow the world up.
Disciples were a failure, entire daa is about cleaning mess that architect caused by awakening darkspawn and civil war he created.
He also attacks the keep and slaughters dalish elves and set enraged mage on humans, specifically his disciples did.
The only thing he succeeded is find a way to free darkspawn from the calling, every his other try was a failure.Assuming he still wants "peace" he is failing very hard, as his journey to black city and tampering with old god.
Well it was clear that darkspawn civil war a problem for him anyway, and assuming he still wants peace disciples are a failure..
1- Not disciples. The Disciple.
Did you try to save Amaranthine city at all?
A darkspawn will willingly seek your Warden and TALK to them in an attempt to warn them about the Mother's plan to invade Vigil's Keep. He's an awakened darkspawn that's immune to the Calling and who's accepted the Architect as his spiritual leader.
The Architect's concoction works. And as stated in the epilogue, should the Warden NOT KILL the Architect, he becomes a leader to the darkspawn, gathers them around and, through his guidance, "the Deep Roads have never been quieter" (quote from the DLC).
2- The Architect didn't order the attack. It was the Withered who went against his orders and attacked Vigil's Keep.
The Architect explains this to your Warden, right before the battle against the Mother. The Architect's plan was TO SEEK HELP FROM THE WARDENS TO STOP THE MOTHER FROM THE START.
The only one responsible for the second attack on Vigil's Keep is the Mother. The Architect never ordered any actions against the Wardens.