No, Davros and the Master have never appeared together on-screen before.
Davros has appeared in:
- Genesis of the Daleks
- Destiny of the Daleks
- Logopolis (as a hallucination)1
- Resurrection of the Daleks
- Revelation of the Daleks
- Rememberance of the Daleks
- The Stolen Earth/Journey's End
-
The Magicians's Apprentice
The Master has appeared in:
- Terror of the Autons
- The Mind of Evil
- The Claws of Axos
- Colony in Space
- The Daemons
- The Sea Devils
- The Time Monster
- Frontier in Space
- The Deadly Assassin
- The Keeper of Traken
- Logopolis
- Castrovalva
- Time-Flight
- The King's Demons
- The Five Doctors
- Planet of Fire
- The Caves of Androzani (as a hallucination)
- The Mark of the Rani
- The Ultimate Foe
- Survival
- The TV movie
- Utopia/The Sound of Drums/Last of the Time Lords
- The End of Time
-
Most episodes of series 8, as Missy
-
The Magician's Apprentice
There are only two episodes where both Davros and the Master appeared; the first is the one under discussion. The other is Logopolis, but Davros only appeared in that episode as a flashack/hallucination, and never encountered the Master.
1 Hat tip to Elliott Frisch for reminding me of this in comments