@Lee: With Sassy I don't outspeed Taunt Jellicent. That´s the main reason (and as you said, Dtail primary purpose isn't doing damage.
Actually, the EV spread is pretty mindless (252 HP, enough sp def for beating +6 Reuniclus, rest in sp atk), and I'm sure there are better options.
And yes, Dragonite is great.
@ToF: Well, if some set upper CHs my Quagsire, chances are that I lose though. And yes, Taunt Jellicent is annoying.