Expose single filter of combination of two fields in views
I eventually got a solution from this. I followed the second primary solution offered although the blogger personally used hook_views_query_alter().


installed the module Views filters populate.
added two filters "First Name" and "Last Name" (both must not be exposed) and added them to a OR filter group (Views 3 supports this). I had to use the operator "Contains any word" for both fields, otherwise the query gave me no desired result.
created a filter "Global: populate filters", added the two fields into this and exposed it.


This gave me a quick solution without hard coding.
Here is other helpful reference.