I agree wholeheartedly with this. There are very few rapiers in my games, mostly carried by elven wizards who may realistically expect to fight other unarmored folks. I made a ruling similar to the whip, where a rapier just can't hurt anyone with an armor bonus of +3 or higher. This lets it stand a chance of hurting folks wearing the low-bonus armors (such as leather and hide) but largely stripping out the higher-bonus metal armors.
That being said, my favorite weapon for druids is the longspear (I'll even take a feat to be proficient with it). With a wolf animal companion, an enemy can't effectively close with you: you get two attacks without it being able to attack your druid at all. Keep a cure spell prepped and you can tap the wolf if it starts to get hurt. Very useful tactic, it's always worked out well in the games I've played.