Special:Contributions should have the same interface for selecting revisions to use RevDel as &action=history does - checkboxes alongside each revision and a "Change visibility of selected revisions" button. At present it only has a "(change visibility)" link for each individual revision, which makes it a massive pain trying to hide a spree of vandalism.
Sorry, I missed this; thanks for the ping.
I was thinking of a page with a workflow similar to Special:Nuke. There would be a form which lets admins filter by username/page/action/timestamp etc and would show the edits and log actions matching the criteria submitted by the user. These can then be selected by checkboxes and submitted with a UI similar to the current Special:RevisionDelete.
The pages which currently use checkboxes+button to link to Special:RevisionDelete would be switched to link to the new page with the matching conditions of those entries so that they can be deleted. I'm not sure how easy this would be to implement as I am not familiar with this part of the codebase.