Margrave (and Landgrave) were considered to be ranked higher than Count (Graf/Grave) and lower than Duke (Herzog).
This is kind of a Jack-of-All-Trades-type card. It's not as strong an attack as either Militia (or Goons, or Followers, or Mercenary), Ghost Ship, or Torturer, and sometimes it's not as strong as Cutpurse or Taxman, but it has the very useful +Buy.
As far as a comparison to other Smithies, this is probably weaker than Torturer but stronger than the non-attack Smithies. It also compares unfavorably with Wharf, as its attack is weaker when opponents have Wharves.
If a board already has +Buy, Terminal Draw, and a discard attack, you can probably skip Margrave. But on boards that lack one of the above, Margrave is a good pickup.