Hey there. I would love to see this little feature.
The percentage made so far up to the next lvl should be shown on the experience bars (maybe with an on/off switch). I know we can see it when we hover above it with the cursor , but seeing it all the time would be nice.
This would be a little psychological benefit.
Greetings
I would rather it show x/x exp than a %, knowing exactly how much exp I get and need is more beneficial to me than the percentage. Keep the percentage on the hover, while having either inside or above the bar show the current and total exp needed.
Thank you for the feedback regarding on (%). It will be sent to our dev team for reference.
Thanks.
i can see why you choose this system. but i think i goes with personal taste.
sooo why not both 
with the option to toggle on and off
Toggles are always great, lets everyone have thigns how they want. An option of /showexp in the chat commands would be fine too, have it show in chat how much exp you get per kill, though that can lag out the system at times. There are various ways to implement the idea, which any way of having it would be fine by me, so long as the option is there =P