I tried to create two macros (Single target & one for the Vulnerable buff), butt this one works better for me (Level 100).
Sequences['MMSi'] = {
specID = 254,
author = "Dagobert",
helpTxt = "Talent: 11?3?11 Step Function 1234",
StepFunction = GSStaticPriority,
PreMacro = [[
]],
"/cast [nochanneling] !A Murder of Crows ",
"/cast [nochanneling] Windburst",
"/cast [nochanneling] Marked Shot",
"/cast [nochanneling] !Sidewinders",
"/cast [nochanneling] Aimed Shot",
"/cast [nochanneling] Concussive Shot",
PostMacro = [[
/run UIErrorsFrame:Clear()
]],
}