Quote Originally Posted by dniem
Tremor works in casting sequence right?
Tremor works on a pulse system. Every couple ticks it "pulses" to break fear. It pulses first when you initially lay it, then every few seconds after. Not worth laying them directly on top of each other as I believe the pulses happen at the same time, but not 100% sure on that so experimentation is probably in order.

So yes, it "stacks". The best bet is to spread the tremors around to provide the largest anti-fear and anti-sleep area possible to prevent getting feared out of tremor-radius.

What I have found that stacks:
Grounding (air)
Healing Stream (water)
All fire (offensive) totems (fire)
Stoneclaw (earth; why would you do this? O.o)
Earthbind (earth; pulse system; best if you spread this out - it's fun to lay earthbind + fire nova in a castsequence)
Poison cleanse (water; pulse system)
Disease cleanse (water; pulse system)
Totem of Wrath (fire; 41 pt ele talent - if you get this you can't get NS so choose carefully)
Windfury (air; pulse system, not worth stacking as pulse is faster than buff duration, so refreshes itself and WF weap can't be dispelled)