Luckily I was able to find a way to fix the issue I'm having. It seems that "Assigned To" is not accepting a value of "domain\username" to be able to be use as a filter. So what I did is I get the userid of the "Last Task Respondent" and use this user id to filter using the" Assigned To" column and it worked!
Never mind. I figured it out. Here is how I did it, if anyone else gets this issue.