FileMaker 12 is slower than 11 across the board. The bug fix updates have helped, but 12 is still slower than 11.
Are the portals filtered? If you incorporate the filtering logic at the relationship level, the portals often update much faster.
Do the relationships use inequality operators? If so and you are using them to define a range of matching values, you might be able to replace the inequality operators with a return separated list of values.
Any of these portals "read only"? If so, you might be able to toss the portal and replace it with a large calculation field that uses ExecuteSQL to list rows of related data. You can specify the pilcrow (return operator) as the record separator and the tab character as the field separator and then use the appearance settings to set tab stops. YOu can even give the field a scroll bar.
I don't really know if this last option will result in a performance improvement--it can result in a much simpler relationship graph, but it might be worth a try to see if it makes a sifference.