Myself and @MySelf approves! 
Anduin Wrynn and Valerian Mengsk are the same.
Their shared skin makes this canon.
Also Widowmaker and Nova.
Stitches and Roadhog.
Raynor and Soldier76.
(Also the Official HotS Comics prove that there are multiple versions of the same Hero, for example, base Alexstrasze and “necromancer” Alexstrasza fought against each other in the war between the RavenLord and the Lady of Thorns.)
I think Deckard is just a powerless old Medivh.