Do damage over time effects stack?

For example, the monk ability Exploding Palm applies a 3-second DoT effect.

If I hit the same target with this rapidly, does the target gain multiple stacks of the effect that each wear off separately? Or do additional strikes just refresh the duration to 3 seconds?

What about two monks that both hit the same target with Exploding Palm?

Solution 1:

As you can read from this guide, there is a stacking of DOTS (damage over time) section about halfway down that states:

Damage over time effects do not stack in Diablo 3. Every time you use the same dot on the same target you do only reset the timer to the maximum duration. This does prevent extreme damage numbers from long time dots. The dot effects are balanced to make good damage over a longer time allowing you different actions in the mean time. They have the best damage to cast time ratio.

You can also find the same text here.

The exception would be DOTS from multiple players. No player can reset/remove your DOT. Everyone has their own DOT counters, so you can apply the same DOT to one enemy as long as it is coming from two different sources.

Solution 2:

DoTs do not stack. If you reapply a DoT before the counter is up, you simply refresh the counter. However, this only applies to YOUR DoTs.

An interesting case where this doesn't fully apply (although this is not necessarily a DoT) is the Demon Hunter's "Bola Shot" ability. If you hit an individual enemy with 3 bola shots, you will get 3 explosions.

Following your example of two monks both using exploding palm, each monk would get his own instance of the DoT. I can say this from experience as my friend and I have played through to Act IV in a co-op both as monks. We both tend to use exploding palm on boss fights, and can see the HP counter above the bosses head accelerate dramatically between No DoT, 1 exploding palm, then application of a second exploding palm.

I couldn't find a blue post totally confirming this, but from the observation of my friend and I through four acts, dots of the same type but from different players apply their own effect for each player.

Solution 3:

No, dots of the same ability don't stack. In fact, to my knowledge there is not a single stacking damage over time effect in the game (as opposed to other effects - the Barbarian's Frenzy for example can stack up to five times).

Dots of different abilites can be active on the enemy at the same time, however.