Shrang and Armarilo said pretty much everything I needed to say but id like to nitpick this line
O.k, your Prankster Taunters are
Thundurus (suspect)
Tornados
Whimsicott
All of those pokemon are not enjoying taking a Dragon Tail to the face AND will hate taking an Ice Beam. So, you are left with Taunters. Right, Lugia has 110 base speed, seriously, your fastest Taunter is Deoxys S and then its, err, Mew. Taunters are hard to find in OU, finding one to outspeed Lugia and take repeated hits (like something not scared of Ice Beam/Dragon tail is pretty hard.
Lastly 90 Base Atk is not as bad as you make out. Granted, Dragon tail is unSTABed, but that attack stat is the same as Virizions or Scrafty so don't dismiss it so lightly
Any set running more than 2 support moves is stopped cold by any any decently fast Taunter or Prankster+Taunt user. Any fast Sub user will also use it as a setup bait. Un-STAB'd Dragon Tail coming off 90 base attack will fail to break most Subs, losing its phazing properties.
O.k, your Prankster Taunters are
Thundurus (suspect)
Tornados
Whimsicott
All of those pokemon are not enjoying taking a Dragon Tail to the face AND will hate taking an Ice Beam. So, you are left with Taunters. Right, Lugia has 110 base speed, seriously, your fastest Taunter is Deoxys S and then its, err, Mew. Taunters are hard to find in OU, finding one to outspeed Lugia and take repeated hits (like something not scared of Ice Beam/Dragon tail is pretty hard.
Lastly 90 Base Atk is not as bad as you make out. Granted, Dragon tail is unSTABed, but that attack stat is the same as Virizions or Scrafty so don't dismiss it so lightly