I find that PitBull AuraBar works wonders with tracking HoTs on players in your raid. It can track both Buffs and Debuffs so can also be used for example to track weakened soul + power word: shield when playing my priest.
The biggest disadvantage of it is it will only track the buffs / debuffs
you apply to the target which when playing disc with another in the raid can get frustrating but for a shammy I find it works a treat. (Unless I have been doing something wrong and it can search for other peoples as well?)
You can see my housemate using it to great effect as a druid
here