I got to 60 without finishing the quest lines in all of the zones. Specifically I never finished Kingsward, barely entered Morban, and not a thing in Steppes or Ashora. I tried to primarily quest - and I tried to get all the carnages out of the way as I hit them. I did a few warfronts and conquests, and any zone events like Volan or Fortress Defense in those high level zones once I was 59. I never used xp vials. It just snuck up on me, really. Fortunately I still have a ton of planar attunement to unlock, so it's worth it to keep working on those (as well as for rep).
and why didnt they tweak this with free2play start?
They did, buy XP potions. I feel that is their answer if you feel it is too slow.
But how I did it was run some random dungeons, doing IA, along with the questing, throw in some random PvP. The rewards from the wins are nice bonuses and the blue loot also helps out a bit. I'm not a big PvP fan and didn't even try doing a match until i was 55 or 56. But once I found a decent heal spec and dmg spec I'm enjoying PvP. Certain maps better then others but it also offers a break from questing.