I've been playing on and off since exodus released. I never tried the round of 10 pigs and fight them all without a weapon equipped to get shield skills. currently my shield skills are like below the 20s and just in the 20s and i have 71 fight skill. So training in the wild is not very helpful for shield skill increases. Shields are one skill that increases very very very slowly.
I think we would all appreciate this being looked at, but it has been brought up many many times and so far nothing has been done about it.