Judge a character based on gameplay mechanics. Riiiight.
Regardless, it's not too far removed from the canon, look at that scene in Shadow Moses where Raiden held back Outer Haven with one arm gone, he may have EVENTUALLY given way, but the fact remains he still held back a massive island sized strong-hold by himself.
Raiden holding back a oversized ship that was also being slown down by the ice it was crashing into, is on a completely different scale.
The force of something pushing and the force of something slamming with all it's weight are two different things. Even if Raiden himself has somehow impossibly quadrupled his strength in such a short time. There's no way that his blade would survive that. And Raiden showed slightly superhuman speeds in MGS4, but now he's capable of running faster than a moving train and so fast that missiles are mere stepping stones for him?
Even works of fiction have their limits. The MGS series has always gotten crazier with each game, but these scenes in MGR are on a whole other level of their own. It's like the crazy jumped up another dozen notches, but in a shorter amount of time. It comes off as being stupid and nonsensical, even for the Metal Gear series.