RS485 uses only two wires and has a protocol for deciding which direction the bus information is traveling, it also specifies how devices in parallel on the bus are addressed so only one device at a time tries to drive the bus.
RS422 is electrically almost the same but it uses four wires (as in your schematic), two for transmit and two for receive. Because there are different wires for outgoing and incoming data, there is no need for the bus direction to reverse. The idea behind the 'DE' pin is it electrically isolates both the transmit pins so other devices can share them. Obviously, only one device on a shared bus should have 'DE' enabled at any time or there would be a data collision.
Your schematic should work. Try temporarily removing the MAX489 and linking the TX and RX wires from the FT232. It should echo back everything sent to it from the PC. If that works, refit the IC then remove the uC and link the RO and DI pins that were connected to it. Again, it should echo back as before. If it does, the problem is in the uC, if it doesn't the problem is in the connections between the two MAX489s.
Note that you only need the terminating resistors at one end of the wire pair, normally the end receiving data.
Brian.