Yeah Tell me about it, but then again I thought the same of Yao Gui and Deathclaws in F3, and by the end I found that I could kill em with Stabhappy (The Unique Combat Knife) without a hassle (Well Except for Deathclaws when they leaped at you and you werent quick enough).
Its all about finding their movements, I find that the Cazadors like to go slightly side to side then lunge, and if you time it right you can smack them with a Melee weapon while you side step the lunge (Was done on a Full Grown Cazador just north of Goodsprings with a lvl 8 character)
Add a second one into the Mix and your screwed. But As Sunny Smiles (or whatever her name is) Says in the Prospector Saloon, "There are Critters up north that just get mad if you shoot em" (Dont quote me on it, its close enough lol)