Does the photo show what your Rubber Plant (Ficus elastica) looks like before being watered or afterwards?
If a healthy plant is wilting from lack of water, it should stop wilting after being thoroughly watered.
However, if a plant is wilting due to damage to it's vascular system, watering may not help. The plant still needs water, but any water given cannot be taken up and may lead to rot.
Another possibility is the water is not penetrating the root ball during watering. Potting soils containing peat can become hygrophobic if they are let to over-dry. Such soil must be weighed down and soaked underwater to re-hydrate.
Does the plant put on new leaves to replace the old ones? All plants will drop their oldest leaves eventually. This is normal, as long as new foliage is being produced at the growing tip. Your plant does look like it may be becoming defoliated. Also, the plant will only retain it's lower leaves if it receives enough light at the base to justify their maintenance.
Recommendations:
• Take the plant out of its pot and examine the root system. Due this after watering. Did the entire root-ball become damp or are there dry areas? If there are, soak the root-ball in a bucket. Replace any soil that floats off with fresh potting soil as you replant.
• After repotting, fertilize the plant with a complete general-purpose again.
• Yes, a brighter spot may help. Near a window as possible. Rubber Plants want bright light. They grow in full sun in the tropics.