Most all the classes tend to be generic and broad, but I guess that's the point.
There won't be any real definition until Jobs are released.

So right now the case can be made that there is a similarity of the present classes to many jobs we have seen in the past.

MRD is like WAR since they both use a Great Axe, have defensive abilities and tank.
MRD is like DRK since they can cure from damage dealt and have weapons with a long delay, and can build a lot of enmity.

I have a feeling once the jobs come out we will again see a blend of abilities from past FF jobs.