No sane warden is going to use this skill in a pvp environment. The only reason to run this skill is for the minor vulnerability. However, having to apply this skill in a combat environment takes away precious time from a burst window. The less time spent applying debuffs the better. That is why most wardens will run a shock glyph to gain the same debuff instead. With the shock glyph, it may not always apply the status effect, but weaving in a heavy attack does a considerable amount of burst damage. Having the shock glyph proc is only a bonus.
Proposition:
Make this skill more attractive by changing the minor vulnerability to "damage done". For example; "enemies under the effect of this skill take x% increased damage from you". This would work similarly to DKs flame damage buff from using its skills. It wouldn't increase anyone else's damage, only the caster. Also, while this effect is active, the bear will prioritize the affected target. This will give wardens the option to use this skill at the beginning of a fight, and not leave them wondering why they even slotted it in the first place. I've gone many times without using this skill because using my burst combo would result more effective. If I had casted this skill first for the debuff, the enemy would've had time to heal and recover from execute range. Speaking of execute, it would be very nice if this skill caused the bear to automatically cast its ultimate when the enemy is in execute range. Perhaps make it 50% hp because this execute does hit quite hard, so as to not make it a death sentence when an enemy is at 25% hp.