What your Imam is doing is wrong and they have to repeat the prayer as it is invalid.

It is permissible to combine prayers in case of rain that is muddy and would wet clothes. But it is not permissible to shorten prayers except for people who are traveling.

The masjid imam in our community pray zuhar as usual and then pray two rakah for Asr as combining the two salat during rain. Although the rain had stopped and the sun was almost out, the imam still combined two salats. The question I have is that he pray four rakah for zuhar and then two rakah for Asr? I only know that one must pray four rakah each salat even when combing for rain. Is the two rakah for Asr ok? should I repeat Asr and pray four rakah?