This is a difficult question to answer as it depend on many other criteria as well. However, if you want to distribute review marks under the criteria you have listed, more weightage should be given to the methodology, analysis and discussion ( the discussion may also be a part of analysis) Outcome is largely depend on those three criteria and language should not be a barrier as it can be even corrected from a outsider.
I m totally agree with Pannilage Upali that the grammatical mistakes should not be any barrier for scientific research article rather then must have to focus on data analysis , relevant discussion and future prospects of work.