Mark, I'd like you to go over your exercise again, with something new in mind now...
when you add or remove an instrument, consider that it thickens or lightens the texture/sound. (not to be confused with simple "loudness")
So when you remove an instrument as the phrase gains in amplitude, WHY do you do it?
I notice that you have the 2nd clarinet hand off to the 1st clarinet... but why not have BOTH clarinets continue playing from that point on? the phrase is aiming towards a crescendo, so you can afford to KEEP some of the sound mass.
And remember, the oboes are pungent, if you are looking for any sort of smoothness in sound over a phrase, the entrance of oboes will MARK an entrance almost like an accent. if two oboes come in at the same time it's even more noticable.
I think that it's important to consider the over-all timbre of a phrase when orchestrating. It the oboes are absent from the beginning, then they should only come in where their entrance will not sound like a pack of rabid kazoos attacking a beehive (no, really I LOVE oboe!

).
In that sense, since you haven't used the oboe tone in the beginning of your phrase, you should probably keep it for the forte climax as a "strengthening" of the overall woodwind tone.