Even if Rand had the blunt dagger, I doubt that the DO wouldn't sense that Rand is using the TP against him. And then the DO could simply cut Rand from the access to the TP; its his essence after all.

I also can't really see the TP as a way of repairing the hole in the Pattern, after we saw how destructive the TP is to the Pattern (I seriously doubt that killing the DO would be the way to win, especially after the end of TGS).

Most Forsaken simply don't want to wield the TP, because it is too addictive and ultimately corrupts & kills you.

Finally, you also aren't allowed to channel the OP at SG. Therefore one could argue in the same way that the OP will be needed to close the Bore (which makes anyway more sense to me).