First, your using the term "cardio" in a pretty generic way. What are you talking about?
Second, in regard to achieving optimal hypertrophy you'd probably be better off seperating weights and your cardio into two sessions.
Third, if your trying to get as lean as possible, that is to lose weight, your not going to grow at your optimal rate anyway.
If you are on gear you can get away with combining the two better than if you were not.
In my opinion, combining the two workouts for an hour and a 15 minutes of exercise (even with 30 min cardio) is not so great a strain that your going to waste away. Considering your diet and training is right you should still make gains just fine. Do you want to be Mr. O, or do you want to do the workout that suits you? Give it a try and see how it goes.