Dragoons already pay for their high crowd control ability with below average warrior armor/ hp and a very minor damage boost over DK's (Who have armor penetrating heavy damage skills). While this nerf does successfully mitigate our strong team utility, it has a similar effect on our already well balanced solo power.
I understand that permanent impale is powerful, however dragoons had trouble in combat with some cc based classes as well as other warrior specs before this change. When people turn and fight a dragoon the numbers are not inherently in our favor. Impale is actually a large part of what makes us able to fight once we have closed the gap between our enemy and us. Impale makes us more mobile than the enemy while we are in the fray, allowing us to perform proper hit and run tactics at the melee level. It also gives us survivability in its FOV reduction that only appears if we stay mobile. Impale is an integral part of the flavor of the class. Looking into solutions, I will assume we are intended to be a bob and weave/hit and run class that really can't just beat your face in by standing there. I am under the impression that dragoons win by being more mobile than the enemy.
The problem arises from the fact that every character has the same base speed. When in team fights impale can be seen as boosting the relative speed of every member of your team against your focus target. In this light, we gave the best speed boost in the game for as long as our stamina held out. It was large, party independent, and distance had no bearing on it.
To remedy the issue, I propose the opposite of what was just implemented reduce the cooldown. Reduce the cooldown to 3.5, duration to 2, and normalizing the damage and stamina costs to be in line with their current counterparts. We could limit uptime not only by its cooldown, but by player skill as well. We have an optimum uptime of 57% so the probable uptime will be in line with the current nerf. The difference is that we can and have to use the FOV reduction and movement slowing more tactically. No longer are we burning all of our stamina in one skill only to jump away before it runs out and be left with nothing to continue on. No longer will impale hit poor casters like a truck. No longer will you be guaranteed to be caught by the dragoon and his team because he hit you with one skill. The class now takes a level of skill and actions per minute more in line with the tactical advantage the dragoon brings.
Other options considered were replacing the slow with a short duration stun or providing a light damage bleed to prevent proper sprinting. Both of these have merits and problems that extend farther into herocraft pvp than the scope of this thread.