I have GW:P and GW:F. Sometimes I need to buy a skill for a character and from here the quest starts for looking where to buy this skill, cause most skills I know where to get, but some more uncommon skills I simply dont know in what chapter the skills appears. So hopping to Kaineng Center to Lion's Arch to Ember Light Camp. Can you imagine when we would have 6 chapters?
My suggestion is to have a skill trainer in Bathazar's Temple where you can buy all skills available for your profession.
Buying skills
sakura75
master_of_puppets
Um.... its called the internet. Hop on, you can look up what skill you need and its location real quick. This idea would make other skill trainers pointless as you can just go there once you have LA or whatever and get what you need. And GW is probably gonna be dead by the time there would be 6 chapters...