They started off as an undefined threat in EaF then when they finally appeared they were more Keystone Capitalists, beneath the Federations enlightened society using money and seeking personal fortune.
The Ferengi Marauder when it fort appeared was formidable- a large weapons pod unfolded from the top and the main hull extended huge claw-like things. The ship was capable of combat, but we never saw it actually in action.
I can see each ship more like a corporation- run by a Daimon who does have to answer to the board of Directors (Crew). Each looking out for it's own best interest, but if there is a threat powerful enough they could not negotiate around then the ships would unify along the lines of the Privateers in old days. While they may not be strategic thinkers, in a battle where each ship performs independently, tactically they would be quite effective.
True Ferengi power comes from their cultures ability to find out what somebody wants/needs and take advantage of that opportunity by providing it. It is no wonder that civilization had flourished for 5,000 years...