My current system includes an all channel antenna similar in performance to the HD7015. It's Aimed south at the main local group of towers. I reliably receive two signals from the north... 70 miles distant.
The difference in gain front vs. back of the HD7015 (and the lager 7080, 7082 and 7084) would start to balance the difference in signals levels (CH 9 & 13 vs the others in the opposite direction.
When you examine the specifications of the 7015,
http://www.winegarddirect.com/pdf/spec_PR7015.pdf, you find that at channel 9 the antenna has 7.5 dBd forward gain and a front to back ratio of 12.5 dB. This means that the the antenna has -5 dBd gain to the rear. (7.5 - 12.5) The signal strength of CH-9 is predicted at 59 dB above the minimum ( 59.1 dB NM). Negative gain of 5 dB leaves you with a NM at the antenna terminals of +54.1 dB... that's a very strong signal... in no need of amplification.
I won't argue against a rotator beyond saying it will double the cost of the system and it can be added later if not done at the time of original installation.