You will need Simulation Craft for this. If you haven't used it before read this first (
http://altered-time.com/forum/viewtopic.php?f=2&t=620" target="_blank)
If you want to quickly see if there are breakpoints for certain stats, import your profile via the armory (or Ask Mr Robot if you prefer). Then use the 'Plot' options to see how your DPS would change if you had 500 - 1000 more points in each stat you select. Keep in mind the more stats you choose, the longer the sim will take to finish. You can then use the reforge option to see how your DPS would be affected if you swapped one stat for another. E.g. Crit in to Mastery. This is useful because while you might have one stat growing faster than another after a certain point, you may loose more DPS than you gain by taking away from the slower growing stat.
If you can see certain points where you think you want to try and hit. E.g. If you swapped some MS into Crit or you just want to see the difference between running with the Icy Veins glyph and without then do the following (don't forget to untick the plot and or reforge options to speed up the sims again (unless you want to see those results again with the changes taken into account)).
At the bottom of your character profile add the line:
copy="Test_Mage"
You can put what you like between the quotation marks to make it more meaningful for you. E.g. I might put Chev_NoIcyVeinsGlyph. Then under that line, put the lines you want to change. E.g.
glyphs=polymorph/icy_veins/ice_block/momentum
But remove the "icy_veins/" to test without icy veins glyph. You can also try swapping out gear / enchants to change stat levels around to help you hit those breakpoints. E.g.
finger2=spellbound_runic_band_of_the_allseeing_eye,id=118306,enchant=50mult
becomes
finger2=spellbound_runic_band_of_the_allseeing_eye,id=118306,enchant=50crit
When done, press the simulate button and it will use the main profile and swap out the lines you have changed for the second profile and run them side by side so you can easily see how they compare. Once done keep playing until you are happy with your results.
E.g. If I was removing the glyph and changing one of my ring enchants to crit, I would have
copy="Test_Chev_NoIcyVeinsGlyph_50CritRing"
glyphs=polymorph/ice_block/momentum
finger2=spellbound_runic_band_of_the_allseeing_eye,id=118306,enchant=50crit