Another way to do it..
That isn't too powerful as I feel so far all the 2[w]+str are.
And these things shouldn't be too complicated.
Power Attack
Fighter Attack 1
You focus your raw strength, into a wild but inaccurate brutal attack.
At-Will * Martial, Weapon
Standard Action
Melee weapon
Target: One creature
Attack: Melee weapon vs. AC +2
Hit: 1[W]+4 power damage + Strength damage.
Miss: Your next movement is limited to 2 squares, this lasts until your the end of your next turn.
~~
This packs a reasonable offset, opponent gets +2 ac, you get +4 damage, and if you miss, your next move leaves you slowed as an offset.
But this is just an opinion.