My NX5510 is a 2016 (late) and I've got 675 hours on it. Zero engine or drivetrain [HST] issues, and I've worked it plenty hard. I've also maintained it well [KEY! - I document all work]. Biggest issue of concern I've had with it was with leaking rear diff casings- having bought new, these were taken care of by the dealer. One could, I suppose, live with the leaks, but if one couldn't then it might be a fairly costly repair item (something that I'd think hard and long over whether I'd do such work myself). All it takes to make a good deal a not-so-good-deal is one major issue: find out your main hydraulic pump is crapped/crapping out, or your transmission is crapping out, and repair costs plus headaches and you find yourself on the bad side of the ledger.
My B7800 had 748 hours on it when I bought it and it was only about 4 years old at the time. It had been used commercially- bucket had been replaced by the dealer (read "a LOT of loader work"). This was my first tractor. Looking back I can see that this was more risk than I'd be willing to take today.
1,200 hrs on a four-year-old machine seems high, likely used commercially, likely worked hard (on the abuse side of things- some tractors, such as my B7800 can take severe abuse [having put on 1,100 hours on it myself I can attest to this!], while others not; and with newer tractors we don't have the data to know for sure).
Mitigation strategy for potential issues with used equipment, given that the tractor in consideration specs out to meets one's requirements, my preference would be an older tractor with fewer hours.
Service documentation! Service documentation! Service documentation! If not, then one really should have some sort of warranty (if dealer). Without either of these a "cheap" tractor can become a project unto itself: last thing I wanted was another piece of equipment, a primary one, that came with unknowns- the reason why I bought my NX5510 new.
The Kioti NXs are a good tractor: time will tell whether they move toward the "great" side of the spectrum or toward the "no-so-great" side. Good tractors, however, can be turned into bad tractors via poor maintenance and or abuse.
Highly recomment SSQA and remotes.