Doesn't matter one bit who has done what in the past as far as leveling is concerned because NONE OF THAT IS VALID ANYMORE.
What matters is what the SP is like now. What I can tell you now is that group grinding blows all the other options out of the water in the 20s at the very least. There's literally no point to even bothering with guildleves and behests because in the time it takes to go get the leve then go back to the camp you could be killing stuff and grouping with other folks you see killing and getting more SP than you'd have gotten from the leve in the same amount of time and then there's the fact that grinding is sustained EXP. You don't run out of 'grind leves', you just keep killing. Unless you want guild marks you are wasting your time.