It's definitely worthwhile to faction grind instead of going through the quest properly. You can basically start whenever you want to, though you'll need to be level 46 to go to Plane of Fear. The three main ways to faction grind are (1) do the tiny gem hand-in repeatedly (2) do the woe/envy/marr part repeatedly (3) do the CoM pages repeatedly. I would personally recommend (3) since you can EXP in CoM while you're at it.
You will need a guild's help to get the child's tear. The final fight isn't too hard and you could do it with a solid 6-man group, I think. You might want to join a guild at 46 anyway just because there are casual guilds out there that don't expect your playtime to be huge and will be a fun experience for you, but if not, you can always ask guilds to tag along and loot extra tears that drop.
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