Don't have a huge issue with Drago (don't care, spelling it this way). Yeah, I personally feel that his story smacks of poor self-editing, but over all he isn't that bad.
That being said….
Space Wolves defeated Magnus, both daemon primarchs.
Yes. Space WolveS
. Plural, as in a many of them, and large number of them ended up either dead or really fucked up. With Drago (don't care), we've got one dude pulling off what it took a Great Wolf (it was a Great Wolf, right?), a previous Great Wolf in a giant metal death machine, and a load of their buddies to do. And, again, most of them ended up very dead. Also, it should be noted that the Great Wolf, Ironhelm, landed a drop pod on the cyclopean douche before fighting him, and even then he still died. Drago, however, just up and carved his initials into a primarchs heart because he got angry. One reads as an epic battle to beat a truly imposing enemy, and the other some form of bastard child produced by poor editing and a nerd-boner induced typing frenzy.
Though I haven't popped open either of these books up in almost a year, so I could be wrong about damn near all of this.