I didn't mention the most unusual part of the gearing on my single bike - I'm running a "super-compact" double crankset with 28T and 46T chainrings. Because of the 46 tooth big ring, I need an 11 tooth cog to achieve a similar gear as your 52-13, which I agree, you really don't need anything more than that (I can still pedal up to about 55 kph / 35 mph, which is plenty).

You may wonder why I'm using such an unusual chainring combo. Well, I did have a triple, but decided there was too much overlap and not much need for the biggest gears, so I replaced the 39 and 52 tooth rings with one 46 toother. I saved about 80 grams in doing so and simplified my front shifting tremendously. Now I can cruise around on the 46 tooth ring all the time until I find a significant climb. It has similar advantages to a regular compact double, but allows a good range of gears at a high cadence for someone who is not insanely fit (I've tried a standard compact double, but I really didn't like the gear options that you end up with). It's hard to find an appropriate crankset to mount the 28-46 tooth combo onto. I've done it using the inner and middle positions of a triple crankset, this would normally cause some chainline issues, but its OK because I have a Jtek jumpstop installed inside the drive-side BB cup, which also prevents me from losing the chain when making the jump from outer to inner ring. I originally got inspired by some discussion on the Long Distance Cycling part of this forum to give this a try, and I love it so far (except for needing one more cog on the cassette). I've done a similar thing on my touring bike, where I've gone with 26-42 chainrings, but I won't do it on the tandem, because as I said above, we need to keep the pedal cadence somewhat smooth when doing front shifts.