The Slayer stances only benefit normal attacks, but Wicked Strike can be used in place of a melee basic attack.
Or can you even use this ability? I was using the character builder on the D&D Insider website, using a human, and it lets me pick one of the normal fighter abilities for his third at-will, so I'm not sure if it's just confused.
No, the stance specifically says that it interacts with melee basic attacks. Wicked Strike is not a melee basic it is used in place of one. Since the stance is not the power generating the melee basic it should not grant a bonus when Wicked Strike is substituted in.
No
Wicked Strike reads:
You can use the power in place of a melee basic attack
Which means that when the opportunity to make a melee basic attack presents it's self, you may opt to use Wicked Strike in place of the melee basic attack, but in doing so it does not inherently become a melee basic attack, and so the Slayer's melee basic attack damage bonus stances do not come into effect.
Were the power to read
This power counts as a melee basic attack
You could make a good argument that the Slayer would get to double dip.
