I think you're used to really large displacement engines, or cars, as the RPM range of the VN750 is not considered high by any means. If you are comparing it to 1500cc cruiser engines, then of course RPMs will be higher in general. Compare the VN to similar sized bikes of the time and the RPMs are similar (shadow, virago.. etc). It's just how the engine was designed, and to be honest, could probably be ran at or near redline for 1000s of operating hours without any adverse affects. The engine was designed for it.
There is no overall design flaw to speak of. Stators failing at 15-30k are super common for any 80s motorcycle. The design of the rectifier (shunt style) also contributed to this, but again, that's just a byproduct of the age of the bike. Newer MOSFET style regulators are easier on the stators, and they last longer. I think the biggest "design flaw" is the fact you have to drop the engine to swap it, as it is a serviceable item. You could criticize them on the regulator placement, though, as it does get hot in it's stock location.
Overall, any bike of the age would have the same issues. I even had to do the stator and rectifier on my wife's 99 VFR. Sure it had 75k miles, but still.. same thing.
1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Rebuilt Forks w/ Progressive Springs
VN750.com Grill Cover
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R
1990 Kawasaki Vulcan 750
1998 Honda VFR800 FI
2014 Honda VFR800F
1989 Pontiac Firebird Formula 350