Hi, I just came back from Taiwan last week, and I covered all the places within 11D10N. My itinerary is as follows:-
Day 1:
Taoyuan Airport > Hualien
Day 2:
Hualien > Cingjing
Day 3:
Cinging > 九族文化村 > SML > Taichung
Day 4 & 5:
Taichung (But Day 5 I stayed at the 汽车旅馆)
Day 6:
Taichung > Taipei
Day 7-9:
Taipei
Day 10:
Jiufen > Shifen etc
Day 11:
Taipei > Taoyuan Airport
A lot of people were commenting that I should go Taichung > Cingjing > Hualien > Taipei. So maybe you can take this into consideration?