No, powers that let you shift as an REACTION don't negate attacks.
There are two different kind of immediate actions: Immediate Reactions and Immediate Interrupt.
- Immediate Reactions powers happpen AFTER the action that triggert it has been resolved.
- Immediate Interrupt powers occur BEFORE the action that triggers the power.
When you are attacked and use an Immediate Reaction you resolve the attack first and then the Immediate Reaction.
When you are attacked and use an Immediate Interrupt you resolve the Immediate Interrupt first and attack later. Now you might not be a valid target anymore or your AC/NAD is to high so now the attack might miss.
Snarling Wolf Stance: Reaction, so happens after you have been hit or missed.
Vengeful Parry: Interrupt, BUT you have to slide the enemy adjacent so this won't get you out of melee range.
Fox's Cunning: Reaction, this happens after you have been hit or missed. You can shift and MELEE attack him back, so shift adjacent to him or you have to have reach when you shift away.