Area damage over time

Area damage over time (ADoT) skills are skills which inflict periodic damage in an area. Examples include Fire Storm, Flame Trap, and Balthazar's Aura. Area health degeneration skills are also sometimes grouped with area damage over time skills due to similar functionality; however, they are not technically area damage over time skills, as degeneration is not technically damage.

NPC scattering behaviour
ADoT effects can cause NPCs to scatter. This generally isn't a concern in Normal mode, as NPCs can take quite a few hits before scattering; however, in Hard mode, NPCs scatter far more quickly.

Though the scattering behavior is generally a problem for elementalists using skills such as Savannah Heat or Breath of Fire, the AI can be taken advantage of to break aggro on a cluster of backline characters, particularly if it is cast in advance of actual contact.

Using Water Magic hexes, such as Deep Freeze or Ice Spikes, on foes before casting ADoT skills can help keep them in the AoE.