"Move page" is 85% slower in Confluence 5.10+ than in 5.8.18, making moving large number of pages very inefficient

We are developers of the Archiving Plugin for Confluence.

Our add-on batch-archives pages by moving them between spaces. Our customers frequently archive tens of thousands of pages in one go, sometimes even more. "Page move" does not need to be hyper-fast, but is expected to be complete in tens of minutes or in some hours most (overnight) even for this scale of data.

"Page move" has been a fairly fast operation in Confluence 5.7, and it became significantly slower some time between 5.7 and 5.10. (As far as I know the "Move page" feature has been rewritten in some Confluence version released around that time.)

Our profiling results:

1555/40 = 39 page moved per minute in Confluence 5.7
400/66 = 6 page moved per minute in Confluence 5.10

6/39 means it is 85% slower than it used to be!

Is there any chance to accelerate page moves in Confluence core?
Or offer an API to batch-move multiple pages? (Currently, the API limits us to move one page at a time.)

*Update 02/06/2017*

Joint investigation by aron.gombas and psemeniuk (see comment thread below) showed that regression happened somewhere between 5.8.18 and 6.0.1:

Regression is present both in memory consumption and cpu usage. As Aron proved increasing memory brings page move time by 30% but it still not up to par with what it was.

Possible area is either `DefaultRelatedContentRefactorer` class or it's clients.