Excluding the warlord. Please go to one of the other million threads for warlord related arguements both pro/con.
While one could argue for pruning a few classes out some are fnd of safe because they are a fantasy archtype and are used in other non D&D related games. Paladins and Rangers for example could probably be merged into fighter but then again you could probably reduce D&D to 3-4 classes if one tried that hard. Paladins, Rangers and Druids in the D&D sense predate D&D though and turn up in fantasy literature, video games etc. The following classes I think are weak concepts.
More of a job description. Anyone can be an assassin and currently right now it is a Rogue scheme. The class went bye bye in 1989, came back as a kit and then a prestige class in 2000 and as a class in 4th ed in 2010? Not sure on the last date feel free to help me out.
Name implies a lifestyle this class has been different in 4 versions of D&D. The rager/striker angle is a 3rd ed and 4th ed angle on the class. The raging one can easily be a fighter via a feat.
The illusionist was folded into the Wizard class back in 1989 and kind of became extinct in 2008. The Sorcerer in 3.5 was a varient wizard and was a striker in 4th ed but still really a wizard. In fantasy literature the words sorcerer, wizard, mage etc are almost interchangable. Pathfinder made the class a bit more interesting but it is still really a wizard varient.
Fear is the Mind Killer