I been reading the posts of napoloen and I do agree what he says.
If a paladin were to attack napoloen with his sword, napoloen will attack him back. But how? One of the things he will do
is to try to make his weapon(the sword) less effective) He might make the paladin drop his sword, or give it to him, or even try to destroy it.
The sword is one of many weapons the paladin might use.
The druid/sentinal has a groove. It can be a weapon too. If a druid/sentinal attacks napoloen, he will again try to make the weapon being used against him less effective. He might set a fire to it. To make it less effective. How is this less effective? one reason is the herbs in the druid/sentinels groove is killed. He uses the herbs in his potions that he is using to help him defeat napoloen.
The herbs being killed only effects the attacker as i am sure that no other druid goes into another druid's groove to pick his herbs since that is the equivant of taking items from a person's house. I am sure that a druid has respect for another druid's groove.
I don't know much about groove but ovious a fire is very dammaging besides the herbs. The groove might still work but it is less effective. If the druid attacks with his groove, then he has to face the consequences and the posiblity that his groove will be destroy(a weapon) just as a paladin faces the risk of loosing his weapon when he fights

Penned by my hand on the 3rd of Scarlatan, in the year 243 AF.