According to the history of the Kaldorei empire they created vast roads and byways across their empire, linking their holdings - the Sundering likely swallowed up much of this evidence for both Night Elves and Trolls alike. Based on how Occuleth is generally treated (like a crazy person, to put it likely) I was of a mind that Telemancy was considered a very obscure branch of Arcane science - very powerful as we now know, but rare as a course of study. It seems like it was considered more dangerous then than it is now (since Mages know much more about the structure of reality in the current age) - hence the use of aids like Telemancy beacons and the like. What portal travel existed in the Kaldorei empire seemed more or less "fixed," and was probably the province of those interested in the art or for emergency usage, not a commonplace method of travel across the empire.
The Kirin Tor seem to have rediscovered and expanded on concepts the ancient Night Elves knew (such as Telemancy) in the creation of their own portal networks. There are of course tricks and concepts they never knew (as shown by Occuleth's mastery of the discipline), but the Kirin Tor also expanded the discipline such that even Occuleth is impressed by some of their feats of portal magic, as shown in his dialogue with Khadgar about Dalaran.