Yep, that's fine.  The results are interesting.

1) Do you often/very often search by a SentDate range?
2) Is a 1 year range typical for a date search? What % of rows is that?

If answer to #1 is yes, I'd consider clustering on SentDate instead. You could add Sent_ID and Seg_ID if you want to get a unique clus key.

You'd keep the same PK, just make it nonclus.

You'd have to decide if you need to add Sent_ID and/or Seg_ID to the DocType index.

To try this, the steps would be:

1) Drop index IX_Sent_01
2) Drop index IX_Sent_02
3) Drop constraint PK_Sent
4) Create clus index on SentDate [or on ( SendDate, Sent_ID, Seg_ID )].
5) Add constraint PK_Sent: ALTER TABLE dbo.Sent ADD CONSTRAINT PRIMARY KEY NONCLUSTERED ( Sent_ID, Seg_Id ) ...
6) Recreate the DocType index (IX_Sent_02).

Btw, you have a lot of clustered index scans on other tables in that query.  You should probably review the indexes on those tables as well.