I don´t know. Maybe the Banshees and Swift Strikes have some better stat combination that prevented them from getting killed. Or maybe some algorithm in the game causes Dimensional Ruiners to be considered `high priority, must be destroyed first` by ranged troops so they were attacked first. Did the enemy use any ranged troops? Better yet, post the battle report.
No the ruiners take all the damage...First GOS were used in the rainbow defense strategy now Ruiners take its place even if Gos are there so only the Ruiners die as they have better stats and take long time to die and until then the attack could have killed the defender