@Greg:
That's a great question. But before we consider their strength, who knows for certain whether or not the storm was just 'luck'.
I seem to recall another character on the verge of death who was also saved by a storm.
Was it luck?
Or something…else?
Now since the narrator tells us this information, it's tough to think they would lie to us, but if there was something else involved, they haven't lied as so much told a half truth.
Now lets consider that Shiki's massive crew wasn't set upon by a storm.
Shiki, although a bit insane, seems to fight with some form of honor if not simply respect for strength (strong world?) I wonder if even WITHOUT the storm, whether he would have unleashed his full power if he lost directly to Roger.
All interesting things to think about.
Yeah ZKaiser and I have both already said we think it's Dragon.