Got myself an epic elemental bow of earth on live the other day and I have been noticing that the greater acid arrow only shows damage when im not actively shooting the target.
It appears that the re-application of the dot every hit, prevents it from actually performing any additional damage unless you stop attacking (or change targets).
Now with the new items having similar dot effects (godly wrath) if this is not working as intended perhaps it needs addressing before you push out more items with like affects for them only to be ignored from a DPS standpoint.