Well yes, Admirals will get personally involved to stop them. Admirals, and not Buster Calls. The Gorousei will just put an Admiral or one the Shichibukais on the Strawhats' asses and be done with it. What are they gonna do, cast a Buster Call on every island the Strawhats were seen, and if they flee they'll destroy another island, and another, and so on… Doesn't make sense.
It makes perfect sense.
If you harbor the strawhats you are an enemy of the government. If you are an enemy of the government, you get buster called.
Being at war with any world superpower means more than that superpower just physically going after you. It means that that superpower is going to eliminate your resources and try to make everyone shun you as well.
Tactically, the threat of a buster call on any country harboring them makes perfect sense, and they can easily justify it as "that island was supporting a stated group at war with us, the world government."
By the way, you keep stating how Oda will run with it by acting like if they don't defeat the buster call now and it can come again, all the series will be is a bunch of marines chasing the strawhats….
I'm glad you're not Oda.
What's a bigger threat to the world government than a group of pirates that literally declared war on the world government, sacked one of its islands, and has the only two people in the world who know how to find/create Pluton on its team? Oh, not to mention this crew destroyed their elite secret assassins, and directly assaulted thousands of marines, and escaped a buster call that's meant to kill everything without fail.
It would be irresponsible for the world government to see them as anything but threat #1.