So really, the only question is: Do we raise the FoS damage to 4[w] or not?
Well, let's compare FoS to the other four Fighter PP 20th level exploits.
Still operating under the assumption that our typical 20th level fighter's healing surge value is 37, that he's wielding an oversized Maul (9 average damage per [W]), 23 Strength (+6), and a +4 enhancement on his weapon. That would make FoS damage average 83 if it does 4[W], 74 if it does 3[W], and 65 if it does 2[W].
In contrast, with Indomitable Strength, an Iron Vanguard will be doing an average of 42 damage, plus pushing the target 1 square and making him dazed.
With Weaponsoul Dance, a Kensei will be doing 34 damage to one target, 26 damage to the next target (assuming he hits the first), and 18 damage to a final target (assuming he hits the first two.) In addition, all three targets will be prone and immobilized until the end of the Kensei's next turn, and the Kensei got to shift a total of 10 squares during his standard action.
A Pit Fighter using Lion of Battle will do 42 damage to one target (with a possible 26 extra damage if the target is bloodied, bringing the total to 68, since you'd probably never use that power against a non-bloodied target.) He also gets to potentially cause every enemy within 5 squares to move its speed away from him.
Finally, a Swordmaster using Crescendo Sword will do 21 damage against enemies in a burst 1 area if he's using a bastard sword, 23 if he's using a greatsword. In addition, he gets to recharge either a daily or an encounter power he's already used.
So, if FoS does 3[W] or 4[W] it will do significantly more damage than any of the other comparable powers. However, they all have an ancilliary effect that makes them more valuable, and, most importantly, none of them come with an associated cost. I'm honestly not sure how to balance all that out. How much extra damage is balanced by the 2 healing surge cost? How much damage is a special status effect worth?
My feeling is that FoS could either do 4[W] plus HS damage, and be fine there, or do 3[W] plus HS plus push 2 squares or something and fine there as well.