The realm is many, many years old. All older players are already fully geared and with nothing to do. Thus, they just run around and gank. The fact that the realm is constantly full every evening does not help either. It was absolutely the same on another server. The only thing you can do is to avoid highly-populated zones and aim for the less popular ones, at least to the enemy faction.
I play mostly Horde, so I always pick Barrens > Thousand Needles > Arathi Highlands > Feralas > Hinterlands for my 10-55 trip instead of the extremely toxic Barrens > Tarren Mill > STV > Tanaris > Un'goro. Barrens is a Horde zone, so you cannot be ganked in it and you can safely reach 25 there, even on 1x. Thousand Needles has no ally posts so the only allys you see there are passers for Tanaris. Feralas is extremely bad for ally questers, so they just don't go there, same as Hinterlands. No, the traveling time is not that long. You get mounts at 20 that cost so little that you can afford them just by selling trash from mobs.
tl;dr - shush and just keep leveling, it's like that on all levels and it will only get worse.