I don't really see how a measly 25% chance every 3 seconds while you even HAVE plague strike on you is such a big deal. That means every 12 seconds, a DK effectively removes one Hot out of your what, 5 possible hots now? You're telling me this is the gamebreaker, the one thing that's completely ruining your day. Please...I'm an 80 DK and you should be bitching about other things before that crap. How about it give us HP back or simply deal more damage. Then you'd probobly see your real problems, like gargoyle.
Kiting a DK is incredibly easy. Considering they have NO WAY to get out of a root, and their only stun is if they have a pet. Even if you get deathgripped you can still walk away from a rooted deathknight, regardless of speed. You can follow up with a cyclone to, and pretty much ignore him. The best druids typically can keep a DK off them long enuf to cyclone w/o a dot on em and stealth. You can also sprint and counteract the snares.
You just need to stop panicking when you see one, that's why 90% of the people who die to deathknights die miserably, they don't know what to do. You'll learn, or die over and over again trying.