Try this

#showtooltip Polymorph
/assist party1
/clearfocus [modifier:shift]
/focus [@focus,noexists]
/clearfocus [@focus,help][@focus,noharm]
/stopcasting
/stopmacro [@target,noharm]
/cast [@focus,exists,harm][@target] Polymorph

Once you cc target A, your tank and dps can pew pew target B, and continue to cc A. Use shift + cc key to polymorph/hex new target selected by tank.

Macro obtained from icy-veins