Yep, it certainly looks to be a design issue. From what I understand, the tubes were rubbing together and also against those retainer bars. This provides some info:
It sounds like there is too much space between the tube support plates. As the steam is generated and flowing, the tubes were rubbing agaist each other and created the wear (not enough pipe hangers ). Like everything, there is a trade-off. More plates means more pressure drop and more cost, but steam generators are very expensive and safety is very important, so it isn't like they tried to save a couple bucks by using fewer plates. I don't know if they will replace the generators, do something to repair them, etc.
The average steam velocities should be well known. It is a function of core power and water properties. There may have been some local velocities that they didn't get modelled correctly. It seems that there was some aspect of this design that was overlooked. It takes a lot of people to design something like a steam generator, but I guess this issue snuck by. It is a whole other thing if someone did it on purpose (signed off on a design they knew was bad, etc.). In the nuclear industry, this would be not only losing your job, but you may end up doing time in federal prision. Nuclear power is governed by federal regulations, so you really get in trouble if you try to cheat.
It would be nice if they can bring them back online. Right now, nat. gas is cheap and probably has been used to fill the void. However, if gas goes up, I bet your rates will go up with it.