Major Revision on Experiment Conducted
The editor has not rejected because (s)he believes that the shortcomings in your paper can be tackled by you. If this entails performing experiments, then further acceptance will be conditional upon that. 

Whether or not you should do these experiments is a different issue and requires knowledge of the case- perhaps you can write a good rebuttal and justify why these added experiments are unnecessary. In general I would recommend against this, but you and your co-authors must make this call based on the issues raised.

Don't think that the editor will necessarily override the reviewers. You need to satisfy the reviewers, either through corrections, rebuttal or a combination of both. Once reviewers are satisfied, editor will be more inclined to accept.