Those of you who know Dave Batista will understand the choice in casting. The character of Drax is a big and aggressive superhuman - something that the hulking Batista could easily pull off in terms of his stature.
The main issue with this casting is that director James Gunn and the Marvel Studios team are casting talent from various backgrounds whom are tried and tested in other fields as opposed to film, such as protagonist Chris Pratt's involvement in television (namely Parks and Recreation). I'm sure that this may end up being a tremendous production on Marvel's part, but there still lies a hint of wonder as to why Marvel has decided not to cast bigger stars from the film industry.
Stay tuned for further updates on Marvel's Phase 2 film GUARDIANS OF THE GALAXY.