I've worked with both systems, and the H5D brought some great improvements (I now have an H5D-50). Yes, the screen isn't as good as a Canon/Nikon screen, but I wouldn't call it a joke. On the H5D, with a quick button press you can automatically zoom in to the point of focus to check sharpness. It works very well. Can you get to a dealer / retailer and see this for yourself?
As Joe says, you should set the camera to draw power from the battery when tethering via Thunderbolt adapter. I've been using the H system for years, and tethering has always been rock solid. Not sure what other problems you're referencing, but my H cameras have been very reliable. And I love the quality.
Here's a list of improvements that came with the H5D (from
https://captureintegration.com/top-10-things-i-love-about-the-hasselblad-h-system/):
*True Focus II – adds knowledge of and compensation for lens curvature
*In-Camera JPG – provides 10MP/12MP/15MP JPG for H4D-40/50/60 In-Camera
*New Buttons & Top LED Display – improved ergonomically and better weather/dust sealing
*Enhanced Style & Look – I like it, it reminds me of the Retina model MBP. To me, it looks Apple inspired, a very good thing.
*Immediate Focus Confirmation – zoom 100% with one press to the exact point of focus without scrolling.
*New Battery Grip – more ergonomic, roughly same power output on H5D as on previous models, but provides 50% more power on previous HxD models
*New reinforced CF Card Door – much more secure and firm.
*New secure locking firewire port – reinforced, more secure, less stress on connector.
*New GUI for LCD & LED Interfaces – allows further control of LCD from the LED interface.
*Dedicated Profiles Button – upload and share custom user work-sets from camera to camera
(Also, as Joe says, now you can power the back from a small, attached Sony battery when using the back on a technical camera.)