i think due to the fact 3200rpm is pretty high for a 4bt, and no one is running a high hp 4bt there has to be issues somewhere.
i have seen a few marine mechanics complain on other boards about the 250hp marine 4bt being unreliable and NOT durable. they use seawater coolers, and seawater for coolant. but again, its all supposition on my part.
as far as balance, i have always understood that a 6cyl is the smoothest engine, and a v12 is just 2 inline 6's
now again, im not an engineer, but i can see that my 4bt is not as smooth as my 6bt.