I cannot stress enough how much I agree with your sentiment that a Deore ten speed is a sweetspot in Shimano's drivetrain lineup. I currently ride a RaceFace Aeffect with a Deore RD, and the Deore cassette, makes for a pretty cheap and bombproof setup. The only gripe is the riveted cassette, which causes a bit more freehub body scarring than I'd like, so I'll replace that with a SunRace at some point.
That said, doesn't the Deore RD only have capacity for a 42 tooth?
I had similar issues with the One Up post in 170mm, but after adjusting the pressure to be a tad higher (close to the maximum it's rated for if I remember correctly) I've had no problems in terms of travel. The sometimes post sticks ~10mm below the maximum extension in cold and muddy conditions, but adjusting it down-a-bit and up-a-bit fixes that, and that could be explained by a lack of service and a winter / autumn of use. A fellow rider seems to be using that post with no issues though.
People's experiences with that post seem to vary, but I'm lucky enough that the post hits a sweet spot in terms of price and quality for me. Also, the remote is nice and cable installation reasonable.
My experiences with them have been similar. Work as expected, hit rocks at times (at 170mm length). If you ride in very muddy conditions, you'll be grinding the finish down after some time (but I don't think that matters). I'd recommend them.