The problem with a leader based civ is that since most people have a rather short life compared to the timeframe of civ 5, you will end up with one time period in which you are best in, which I'm not a fan of. If that time period is too early, then you feel rushed to capatalize on it, but if it's too late, then it usually won't make much of a difference since you will probably already be dominant by endgame.
Not really. JFD has few to no designs that are very one-dimensional. They get stronger during certain eras, surely (Prussia excels at Industrial Era warfare but can fight at any time and Roosevelt only has his uniques come up in the Industrial and Modern Eras, but his ability can help him a lot). But most of the time normal Civs have a powerspike. England from Medieval to Industrial is a powerhouse, wrecking everything on its path. Egypt has its uniques help a lot in the early game and fall off in the late game a bit, similar with Rome and Greece. But none of them are useless past that point.
Culture and +1
Great People points, For every Declaration of War receive +10%
Tourism from Landmarks, has 3
Great Work Slots and 1 Artist Specialist Slot
Movement in Friendly Territory and generates
Defensive Bonus when stationed on Landmarks.
Connections to the Capital generate +1 and +10%
Production to Cities, Upon completing construction of a
Happiness boost, receive a free Military Unit from Defensive Pacts.
Gold upon defeating an Enemy Unit.