Make a trigger like this:
Type: Aura
Aura(s): Prayer of Mending
Unit: Group
Name Info: Player(s) Affected
Stack Info: Aura Stack
Aura Type: Buff
Own Only
Then under display you can use %n to get the player that has it, %s to see the stacks and %p to see remaining duration.
Code:
dud)baGlLKTrfMlv0SL4MOWTvQ2Ps0Ej7wX(f0pLK(Ra)wkdvPmyQ0WLuNcLQogv5CG0cPeTuukwmkLwoIPPcpf6XuvpNIdJ0uLQjd00v1fPe6BOKNHIUUkAJukgMKyZa2oLGLbIrHsLpl03PKAKuQ6KGQrRegpLKlPK6wukDAuDEvACGYLf9AkvwEQlKle(8jbG6NoH73gJtSolLa7BLBWgHEtsvag5aYN4hPcnc9wDSI1QdH7cbfcQUqqUPUqV90Qx46j0LDRnSp0DDTWNWJXKOUqZt9TlGpanHMN6BNWM1t1PCLLcph(lmsAN1ch6EgWhGMW6c9MeJWHUNg11spHBe6njHUnGqxg5aYNOE9cjzK3M(Tof(PvVqR5G)czdlwqHcPctwmHWeguyWGjaBpCiCo37eEmMeJw6jKdkCJqVjj0Tbe6Yihq(efUi5XfVSXbmhmHCaHPNhlhEqHura2EavyPrbvx4Pjd8luJrwkK0kP6c3plpxD96fEAYGHUNITc9luJrDHg(elPWn2a3IyxVE9cPQlCJqVjj0Tbe6Yihq(efcF(Kaq9tNW9BJXjwNLsG9TYnyJqVjPkaJCa5t8Ju9cTGw6DuPIEj