This is a rough approximation of actual play. This is a simulation of fighting a boss dummy. You will always have lower DPS than what is shown here because you never have perfect 100% cast uptime.
All activatable abilities and items are activated on CD (usually at the start of fight).
The 'Hasted Rotations' tab will calculate the max DPS rotation for the given gear set and at fixed haste levels.
Downranking is not implemented so in mana starvation simulations you will see a high ratio of OOM. This results in lower DPS than is possible if using downranked spells.
If stat weights are fluctuating too much try increasing iterations. Usually 10,000 will remove variability but can take a while to run.