so just recently used imcraft for my first time and so i got my stat weights wich was int>haste>mastery. what i do wonder is that that mean i should go with 80 int+160 haste gems to instead of artful(mastery).?
The problem is, that mastery scales very linear, yet haste doesn't.
There are certain haste points (breakpoints) that increase hastes value whereas inbetween values less.
Simcraft takes the haste you have and more or less just adds 1000 or so rating, takes the result, subtracts your current dps and divides the result by 1000.
If you now for example take two of those breakpoints with those 1000 additional rating, your haste rating will be higher as if you would jump over no breakpoint.
Another thing is: There is a certain statistical delta, which is about 0.05 to 0.1 rating at 10k iterations.
Simple answer: If the difference is small (1.54 vs 1.49) you don't have to worry.
More complex answer: Look out for the breakpoints, get just above one and take mastery thereafter. You can see a complete list of haste breakpoints for all specs here: http://www.totemspot.com/vb/entry.php?b=44