For the most part DoTs come in 2 magic types, Evo and Conj. Evo DoTs contain debuffs of some type and Conj DoTs are strictly damage spells.
Not 100% on this but it's what I go by and don't ever remeber having a problem.
All Conj DoTs stack because they are just damage spells.
Evo DoTs will not stack if they contain the same type of debuff or are of the same spell line as another Evo DoT that is being used. As far as Evo DoTs are concerned the higher DoT will either overwrite or block lower lvl ones.
This rule does not apply to necro snare/DoTs. IIRC these spells are actually classified as a snare and not a DoT so special rules apply.
Quote:
Snare Lines. Two people can stack the same snare dot, but if you can a different one it will replace mine. And I overwrite a Druid snare.. and block it.
Necros and SKs really need to keep this in mind while grouped with a Dru/Rng. Most Druids or Rangers will not continue to snare if it keeps getting blocked by these spells as Dru/Rng snares generate HUGE amounts of agro.