Are Dots a thing?

Hi there,

Do people use a flame staff and spec 9+ dots and simply keep them up? My first calculation for PvE tends to be "I will run out of juice before 20 seconds end but I might deal good damage anyway"

And what about PvP? I mean a player with 10 dots will just hide in some corner and press damage shield right? I will never kill him/her... Right?