Shield are a well coordinated unit. They've taken out John Cena, Ryback, Team Hell No, Big Show, etc.
They would have no issue with Sting or Hogans old ass.
Aces and 8 have not been booked as a legitimate threat. And 2 the story is retarded. Hogan is the GM/Comissioner of TNA, which has a pretty large roster. All he has to do is order all of his employees to bum rush Aces and 8 and it would be over. Throw the stupid bike gang out, take your talent. Or he could call the cops and have them arrested.
Shield are targeting certain individuals who represent injustices. It's not an invasion. They get in, complete the mission and exit like a special op team would do.