[Unit experience] What are the effects?

[bovi]

Since when does defence skill help in all directions? I thought it was clear that it only helps from the front and the right side.

Sorry about that, you are right, only those two sides are helped.

I never run a test, but I don't believe that experience doesn't add to range attack. I had silver and gold chevroned slingers and they annilated everything and I never heard anything different.
The reason the test you recommend doesn't prove that is because EB phalanxes are invulnerable to any range attack from the front, so you are right more attack doesn't help there.

I chose a phalanx unit because any unit except those will either be significantly decimated regardless of upgrades, or they will reach the slingers before they have spent a significant amount of bullets. The test is valid precisely because they are so resistant to missile fire; with only +3 attack from weapon upgrades, they are decimated. Yet, even with 9 chevrons experience, which means +9 attack, triple the amount of the weapon upgrade, they are not.

Go ahead and test it.