Does Oxford ever waive the IELTS language requirement? This question is quite specific but I believe it applies to other school of similar rank. 

I have the following kind of IELTS English language test result:


  Speaking: 8, Listening: 7.5, Reading: 8.0, Writing: 6.0, average: 7.5.


According to Oxford's language requirements, they desire an average score of 7.0, which I do fulfill but also a score of 6.5 for each of the sub tests, which I do not.

With such very subtle mismatch, is it necessary to take the test again? According to the official guidelines, apparently, any offer is conditional until the requirement has been met.

I have four peer-reviewed publications in good venues; will it be of any help? I think the writing test result does not indicate my true level of proficiency.
This is not very specific, I thought you were referring to undergraduate but if you have 4 peer-reviewed publications already then I guess you must be at least PhD level?

In the former case, in my experience Oxford University does not waive the requirements for English and you are probably better off if you take the test again. By the way, my understanding is that you need a 7.0 average AND at least 7.0 in each component.

If you are applying for something more senior (PhD, Postdoc, etc) then it depends on the individual department at which you'd be working.

-edit-
Aah, just seen you tagged this with PhD. The requirements you list (7.0 ave + 6.5 component minimum) are for a Master's degree rather than the DPhil.
To my knowledge the IELTS requirements vary by department (mine doesn't seem to have any, for instance) but it looks like a 7.5 average with no less than 7.0 in any one component is the most common requirement. Based on that you will definitely have to resit the IELTS exam.

You can see the generic requirements here: http://www.ox.ac.uk/admissions/graduate/applying-to-oxford/application-guide#content-tab--3
For a DPhil the 'higher level' requirements would be needed, if applicable to your subject.