You need to share more information if you want actual help. You could also anonymize the plan before sharing it. SQL Sentry has that option.
How to Post...

Decomposing the splitter function might not give the best performance, but it could help in your case.

--Create sample data
CREATE TABLE #Sample ( SomeColumn varchar(1000))
INSERT...

Yes, she's been with me for...

Something like this might work. If I understand correctly.

DECLARE --Parameters?
   @IRN nvarchar(254),
   @DocTitle nvarchar(254),
   @Directory nvarchar(254);

DECLARE @DocName nvarchar(254)...

This is an alternative. It may or may not improve the query (it would definitively not improvise it 🙂 )

With CTE as
(
  Select sd.*,...

Did you check for any blocking happening while testing?

I remember that AdventureWorks has an example on how to do this in SSAS. I don't have it installed right now, but you should check it.
Here's an article from...

You still didn't post the code that you're using.
That's a horrible design and a bad idea. It reminds me of a db horror story that you can check in...