Arimidex is very powerful if dosed correctly. You don't need to take anything else. Also, chrysin may slow down metabolism in some men which is not a good thing of course.
There is another reason as well: when taking Arimidex, you want to be monitored, i.e. have your testosterone and estradiol checked after. Once you get your E2 into the range you and doctor want, you don't want to mess with it. Too high and you have nasty problems; too low and you have nasty problems.
And I'll say the obvious: always ask your doctor before combing supplements and medicaitons. It is very hard to keep up on all the latest interactions and he can look it up in the latest databases.