That's logical, you are getting experience from using a skill. You get experience using First Aid and Doctor right?
Ohh, no, but you can have two chars attacking, crippling and then healing(FA+Doc) each other! ABUSE! EXPLOIT! UNLIMITED EXP! Anything else? -.-
Following your way of thinking, we should remove experience that you gain for healing.
We should remove experience you gain for walking on the map and using your outdoorsman skill! Because now you just walk around, and walk, and walk... And gain exp everytime you get an encounter! You just need about 130% in outdoorsman.
We should remove experience you gain for repairing! Because you could get a cheap armor, and then let the other guy shot you so the armor breaks. Then you repair it! UNLIMITED EXP!
You know how fucking boring is leveling a thief this way? Moving a coin between two inventories, then doing it again, then again, again... ZzZzZz.... Yes, you could use a bot here. And in all the examples i pointed above.
Now, my point of view. Thiefs should gain xp when stealing from players. When you think for a while, you could get soo many ideas how to make this not exploitable. You just need to use your brain a bit harder.