If Rand hadn't been able to channel the TP in the first place, the DO likely either would have turned Rand to the Shadow or killed him outright, in either case more or less ending the conflict. The issue of striking fear in the other Forsaken would have been moot had Semi's plan succeeded, since the Pattern would have unwraveled with the DO's victory. The issue I'm having trouble wrapping my head around is why the DO would have given Rand access to the TP when not having done so likely would have resulted in an early victory over the Light. In other words, why willingly let Rand escape when you have him firmly in your clutches, as was the goal in the first place?