iPhone 5s email deleted from Inbox not synchronizing correctly to Exchange server/Outlook inbox
Well I ended up solving this problem with a slightly lateral solution. Despite the fact that the iPhone was not updating the changes I made while I was offline, it was synchronizing all new changes just fine. Given I wanted to maintain the inbox on the iphone, I just created a sub-folder under the inbox and moved all my messages there (on the phone), that change was successfully sync'd to Outlook and then I just deleted all the messages from the inbox on Outlook (Inbox represented the 450 messages I had deleted on the iphone while offline) and then moved the messages from the temporary sub-folder back into the inbox. Everything continues to sync correctly.

Obviously this is not a technical solution as I had only 75 messages on the iphone inbox that I wanted to maintain it was an easy fix. If anyone knows how you might better deal with this scenario when there are thousands of messages in play I'd be curious to know!