Consider, though, the following situation:
Boss puts out AOE circles under the feet of random DPS. DRG on flank gets circle put underneath them. Boss is too big to run to the other side without pausing attack combo. DRG hits 4th step of combo.
With only F&C, DRG eats potency loss by having to hit from behind with a flank-increased attack or has to delay attack combo in order to reach the other side. Either way, objective damage loss. Or they could keep the stereotype alive and risk eating the AOE.
With WT added, there's a 50% chance that the DRG will get a rear-increased attack, allowing them to keep their combo flow and not eat a potency loss.
So there you go. A situation where having only F&C would have been an objective DPS loss.