Multipath is not a concern if you use a proper combiner. I had the advantage in my area of the one channel being in the opposite direction also being the lowest frequency digital OTA in m area. So I had a specially made Combiner ordered that recieves CH 25 and up on one antenna (A nice ChannelMaster flyswatter UHF) and CH 18 and down on the Stealth pointed towards the other channel. The results are phenominal. Before getting the special combiner, multipath was causing all my signals to be in the 80-85 range. after just swithcing the splitter for a custom diplexer, every channel is 95+ (this is without any movement of the antennas). By having the StealthAntenna for the lower frequencies, I am able to recieve VHF and FM over that antenna as well. I pipe the FM into my home theater stereo, and have never had as good of reception.
Considering, even without multipath, the splitter provides anywhere from 2.5-3 dB loss when combining. The highest loss in recieved ranges on the diplexer is 1dB. Pretty impressive. I purchased the diplexer from tinlee.com.