Well I have owned various Diana products. Both springer and PCP. If you could put problems in a five gallon bucket it would be full. I still own a Classic 350 and a 460 magnum. I have had various problems with both of them, from broken pot metal safeties, to internal cocking shoe problems with the 460.
No one takes better care of rifles than I do, I check them prior to using every time, I keep them lubed and wipe them down with an oil cloth after each use and they hang on racks in the den in open air in a conditioned space.
My most dangerous defect was with a 350 Panther, the one with the synthetic stock. Loved the looks, loved the accuracy, then one day as I was cocking the rifle the rear of the action came flying at supersonic speed at my face, I just barely had the sense to quickly move my head, it still got the side of my neck a bit. On inspection I found that the main stock screw was only two threads deep into the action screw boss and had allowed the force to simply shear the threads. A trip to Fastenal to get the proper screw solved the problem.
If you gave me a brand new 350 today, I would first remove all the sights so they do not fall off, wrap paracord around the stock and rear action until I know it is not going to shear, and go look in my closet for one of the new safeties I have and be ready...........Grin! If a new 460 I would replace the cocking lever pin with the newer hardened pin before I even shot it.
The 350 is a beautiful rifle, long and lean, and very accurate. However if you use it much and I do not consider 2000 shots much, it may or may not make 5000 shots without breaking, I would not bet on that though. My experience with Diana is that another problem will get added to that bucket. Us'ns ole farts and full time shooters develop our opinions on what life shows us for any product. My two Diana rifles are top notch now, however based on past experience I would not purchase another. Your mileage may vary, mine was kinda short before the steering wheel fell off.
Cheers
Kit