Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 24319)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -2208,7 +2208,8 @@
 			if ( ( ( 0 != $left_handle_at && $count < $left_handle_at ) ||
 				 ( 0 != $right_handle_at && $count > ( $right_handle_at - 2 ) ) ) ) {
 				$all_the_revisions[] = array (
-					'ID' => $revision->ID,
+					'ID'        => $revision->ID,
+					'completed' => true, //mark as completed, no need to load diff
 				);
 				continue;
 			}
@@ -2216,7 +2217,8 @@
 			if ( ( 0 != $left_handle_at && $count > ( $left_handle_at - 1 ) ||
 				 ( 0 != $left_handle_at && $count < $right_handle_at ) ) ) {
 				$all_the_revisions[] = array (
-					'ID' => $revision->ID,
+					'ID'        => $revision->ID,
+					'completed' => true, //mark as completed, no need to load diff
 				);
 				continue;
 			}
Index: wp-admin/js/revisions.js
===================================================================
--- wp-admin/js/revisions.js	(revision 24319)
+++ wp-admin/js/revisions.js	(working copy)
@@ -56,12 +56,27 @@
 			}
 		},
 
-		loadDiffs: function( models ) {
+		loadDiffs: function( models, otherModels ) {
 			var self = this,
 				revisionsToLoad = models.where( { completed: false } ),
 				delay = 0,
-				totalChanges;
+				totalChanges,
+				foundModel;
 
+			// in two handle mode, pass the other handle's models and copy over scopeOfChanges (tick width) from that model for positions this handle can't reach (but the other handle can reach)
+			if ( 'undefined' !== typeof otherModels ) { // otherModels only passed in two handle mode
+				_.each( models.where( { completed: true } ), // select just the models that are marked as not needing loading, eg. positions this handle can't reach
+					function( theModel ) {
+						foundModel = otherModels.findWhere( { ID: theModel.id } ); //find the matching position from the other handle's models
+						if ( 'undefined' !== typeof foundModel ) {
+							theModel.set( 'scopeOfChanges', // set the displayed scope of changes for ticks this handle can't get to
+								foundModel
+								.get( 'scopeOfChanges' ) ); // copy the scope of changes from the other handle which can reach this spot
+						}
+					}
+				);
+			}
+
 			// match slider to passed revision_id
 			_.each( revisionsToLoad, function( revision ) {
 				if ( revision.get( 'ID' ) == revisions.model.settings.revision_id )
@@ -69,45 +84,41 @@
 			});
 
 			_.each( revisionsToLoad, function( revision ) {
-					_.delay( function() {
-						revision.fetch( {
-							update: true,
-							add: false,
-							remove: false,
-							success: function( model ) {
-								model.set( 'completed', true );
+				revision.fetch( {
+					update: true,
+					add: false,
+					remove: false,
+					success: function( model ) {
+						model.set( 'completed', true );
 
-								// stop spinner when all models are loaded
-								if ( 0 === models.where( { completed: false } ).length )
-									self.stopModelLoadingSpinner();
+						// stop spinner when all models are loaded
+						if ( 0 === models.where( { completed: false } ).length )
+							self.stopModelLoadingSpinner();
 
-								totalChanges = model.get( 'linesAdded' ) + model.get( 'linesDeleted' ),
-									scopeOfChanges = 'vsmall';
+						totalChanges = model.get( 'linesAdded' ) + model.get( 'linesDeleted' ),
+							scopeOfChanges = 'vsmall';
 
-								// Note: hard coded scope of changes
-								// TODO change to dynamic based on range of values
-								if ( totalChanges > 1 && totalChanges <= 3 ) {
-									scopeOfChanges = 'small';
-								} else if ( totalChanges > 3 && totalChanges <= 5 ) {
-									scopeOfChanges = 'med';
-								} else if ( totalChanges > 5 && totalChanges <= 10 ) {
-									scopeOfChanges = 'large';
-								} else if ( totalChanges > 10 ) {
-									scopeOfChanges = 'vlarge';
-								}
-								model.set( 'scopeOfChanges', scopeOfChanges );
-								if ( 0 !== self.rightDiff &&
-									model.get( 'ID' ) === self.revisions.at( self.rightDiff - 1 ).get( 'ID' ) ) {
-									// reload if current model refreshed
-									self.revisionView.render();
-								}
-								self.tickmarkView.render();
-							}
-					} );
-					}, delay ) ;
-					delay = delay + 150; // stagger model loads to avoid hammering server with requests
-				}
-			);
+						// Note: hard coded scope of changes
+						// TODO change to dynamic based on range of values
+						if ( totalChanges > 1 && totalChanges <= 3 ) {
+							scopeOfChanges = 'small';
+						} else if ( totalChanges > 3 && totalChanges <= 5 ) {
+							scopeOfChanges = 'med';
+						} else if ( totalChanges > 5 && totalChanges <= 10 ) {
+							scopeOfChanges = 'large';
+						} else if ( totalChanges > 10 ) {
+							scopeOfChanges = 'vlarge';
+						}
+						model.set( 'scopeOfChanges', scopeOfChanges );
+						if ( 0 !== self.rightDiff &&
+							model.get( 'ID' ) === self.revisions.at( self.rightDiff - 1 ).get( 'ID' ) ) {
+							// reload if current model refreshed
+							self.revisionView.render();
+						}
+						self.tickmarkView.render();
+					}
+				} );
+			} );
 		},
 
 		startLeftModelLoading: function() {
@@ -186,7 +197,7 @@
 			self.leftHandleRevisions.fetch({
 				success: function(){
 					self.stopLeftModelLoading();
-					self.loadDiffs( self.leftHandleRevisions );
+					self.loadDiffs( self.leftHandleRevisions, self.rightHandleRevisions );
 					self.tickmarkView.model = self.leftHandleRevisions;
 					self.slider.refresh({
 						'max': self.revisions.length
@@ -216,7 +227,7 @@
 			self.rightHandleRevisions.fetch({
 				success: function(){
 					self.stopRightModelLoading();
-					self.loadDiffs( self.rightHandleRevisions );
+					self.loadDiffs( self.rightHandleRevisions, self.leftHandleRevisions );
 					self.tickmarkView.model = self.rightHandleRevisions;
 					self.slider.refresh({
 						'max': self.revisions.length
@@ -242,8 +253,8 @@
 
 		disabledButtonCheck: function( val ) {
 			var maxVal = this.revisions.length - 1,
-				next = ! isRtl ? $( '#next' ) : $( '#previous' ),
-				prev = ! isRtl ? $( '#previous' ) : $( '#next' );
+				next = isRtl ? $( '#previous' ) : $( '#next' ),
+				prev = isRtl ? $( '#next' ) : $( '#previous' );
 
 			// Disable "Next" button if you're on the last node
 			if ( maxVal === val )
@@ -567,8 +578,8 @@
 
 		// next and previous buttons, only available in compare one mode
 		events: {
-			'click #next':     ! isRtl ? 'nextRevision' : 'previousRevision',
-			'click #previous': ! isRtl ? 'previousRevision' : 'nextRevision'
+			'click #next':     isRtl ? 'previousRevision' : 'nextRevision',
+			'click #previous': isRtl ? 'nextRevision' : 'previousRevision'
 		},
 
 		render: function() {