You seem to be encountering the same problem I had early on. I even wrote about it here, but its been vaped.
The problem occurred because I had been going out and doing all the quests but NOT doing the missions, so some quests involved a LONG walk. In fact I found Fort Rannik by adventuring. If I had done the first mission, then I would have ended up at Fort Rannik that way - and got 1,000+xp.
Some final quest locations will be nearer one town than another. It may not be closest to the town where you get the quest. This is particularly true of the ones you get at Piken Square, where the big XP quests are better started from the Grenditch Courthouse (you DO have to trek to Grenditch to find it).
Sometimes it is a good idea to select a quest in your log, then go outside town, press M for the big map, and see how far away the destination is. (The green star will either be the location of the final target or the location of the zone you have to pass through to get to it.) Then map to another town you have already found in that direction, and repeat. You may find that the green star is significantly closer.
It isn't necessary to do ALL the lower level quests. They have added quite a few since the game came out. Some give skills (useful) others just give XP or items (not so useful).
You really aren't missing out in XP if you don't do certain quests. There is plenty available on later quests and missions. And as you have found, if you are too high a level for an area the XP/min really drops because of all those 0 XP kills.
If you advance the game by doing missions, you will enter areas where your XP will be better, and other skill quests are available.
Some skills you will really want, others maybe not so much. It is difficult to tell first time through I know.
I know I spent far too long around Ascalon City with my first character.
Do the first couple of missions, then find Piken Square and Grenditch Courthouse and hoover up the XP/skills
And if there's a better weapon etc you really need, just ask. We can probably find something for you.
HTH
Edit: P.S. When checking final quest locations (as above) you may want to check several other quests too. Sometimes you can complete two or three in an area without trekking there multiple times.