Lobstrok is, at this point in time, merely a texture model within the World of Warcraft file directory.
It is unknown whether or not this was the original name for the Makrura or if this is simply a tribal leader of the lobster-like race of humanoids. However, as the prefix "Lobstrokk" also exists for Makrura related files in the Warcraft 3:TFT World Editor, it is probable that this creature type has undergone a renaming, much like the relation between the Owlbear and the Wildkin.
However, if you really want information, you should reach the Makrura page.