DK Disease Watcher?
Any addons that do this for all mobs?
I actually just signed up to this website to post this x.x
ForteXorcist (ForteWarlock) : WoWInterface Downloads : Warlock
Don't be discouraged by the "warlock" part, it was originally written as a warlock DoT tracker, but also has an inbuilt cooldown bar.
It takes a bit of setting up to get used to, but i like it =)
Of course you can browse for other trackers, I'm sure theres many out there, thats just the one I use.
(BTW, disable the healthstone/soulstone/etc mods if you use it lol)
Elkano Buff Bars will do it as well. You can pick what you want it to show ot not show individually also.
DoTimer is great as well, although you have to bear a little bit with the excess bars during pestilence on aoe packs.
I use two things for watching my diseases... quartz and runewatcher. you can get both from curse.
i do the same as above. Runewatcher is fantastic.