Is it permissible to say "May God have mercy on you, O teacher of the world!" to a deceased scholar?

A Muslim loves the working scholars who follow the Sunnah (definition), and loving them brings one closer to Allah. The phrase "May Allah have mercy on you" is a recommended supplication, and there is no harm in describing a scholar as "the master of the world" if the intention is that he is a teacher and guide for people, while being cautious of the excessive praise and exaggeration forbidden by the Sharia (definition).