Maybe Uniden should incorporate a multipath meter...just like an old school analog FM tuner from the 70's. I use a Kenwood KT-8300 that has one and it helps get the antenna pointed correctly.
Generally, a meter won't help. You will still get out of phase signals an analog based scanner can't handle. Some scanners do include a signal quality indicator you can use to optimize digital reception. But, unless you are very close to and in line of sight of a tower, reception will still be marginal. Directional antennas only help in rare circumstances where all the potential interfering signals are in the null pattern of the antenna.
The other frustrating thing is the multpath reception constantly changes with leaves on the trees, snow on the ground, local weather etc..
I helped a friend set up his TRX1 with a Yagi antenna in the summer and it worked great until winter when he lost reception almost completely on most days. He was fairly close to one tower but had other towers on all sides. Probably with the no leaves to attenuate the other signals and reflections from snow on the ground the Yagi directivity was insufficient to reduce the other signals.
Multipath can generally be dealt with on FM broadcast due to "capture effect" where a signal only a few db stronger will overcome the weaker signals. Attempting to decode a digital signal after it has gone through the FM limiter/discriminator detector circuits on a typical scanner is made worse by the fact that the detector compresses the amplitude of all the incoming digital data from the various sites or reflections to about the same level so it is very difficult for the digital decoder to sort out the mess. The same design that optimizes analog FM reception is detrimental to digital.
While I am on the subject, the FM capture effect works best with wide band FM like broadcast and earlier versions of mobile radio FM. As the FCC repeatedly lowered bandwidth, the capture effect was degraded. With the 2013 narrow banding, what is called the modulation index was decreased to the point that most of the advantages of FM such as signal to noise ratio and capture were severely degraded. This is one of the reasons that digital technology is now more attractive for mobile radio systems.
On a receiver capable of direct digital reception, the DSP circuits can easily sort out the best signal from the out of phase stuff from multiple sources.
Bottom line with an analog based scanner, reception of P25 simulcast depends on location and can vary with season, weather and other factors.