Quote Originally Posted by Assertn

Take mihawk's course starting from the Baratie arc for example....
1) He's in the grand line, where he wipes out Don Krieg ships
2) He pursues Don Krieg to East Blue
3) He meets Shanks in the new world, where Shanks throws a party to celebrate Luffy getting a bounty.
4) He meets with the marine leader in Mariejoa after Crocodile's demise.

So basically he goes from grand line to east blue to new world to the mid-way point?
It's not even just him, either....there's also Ace, who manages to go all over the place to hunt down Blackbeard. Then of course, there's also Buggy and Don Krieg, who have managed to leave the grand line without passing through the calm belt or reaching the finish.
As far as I remember, Krieg never entered the grand line. His crew encountered Mihawk on the entrance, where he wiped them out. His boat must have seastone to be able to move through the calm belt calmly, like the marine ships.

Ace powers up his own boat with his fire, so he can pass through the calm belt with no problem.

Was Buggy ever on the grand line? I mean, sure, he was part of Roger's crew... but we never were told about if he remained with them until Roger became Pirate King... maybe he left just after eating the devil fruit in any of the other 4 oceans... which would explain how come he is so 'weak' compared to other Roger Pirates. Plus, he did not know how to get to the grand line, that is why he was mad when Nami took his map.