The problem with slows is how the math works. The closer you get to 100% the more insane slow gets. Turgur's is 75% and this makes the attack delay 4x. I.e. if the mob unslowed hit every 2 seconds, with Turgur's it hits every 8 seconds. Sha's Lethargy at 40% would make that 2 second attack delay 3.33 seconds. Assuming Togor's is 60% at level 50, the attack delay for this 2 second mob would be 5 seconds. So while them buffing beastlord Lethargy was needed since beastlords don't get their good stuff until Kunark and PoP, it's still not going to make them slow anywhere near shamans or enchanters. Sha's Lethargy is also a level 50 spell so it's a long wait for it.