Everyone may do things differently. We may all have different agendas. Personally, I am leveling everything pretty much evenly with some emphasis on 1 or 2 classes. Classes can support each other when being leveled together - my gathering classes support my crafting classes, and crafting classes also support other crafting classes. Thus, lots of money is saved.

If I am not mistaken, the slope from lvl 67 to 70 is pretty steep, and it's very hard to push without leves. With my approach of leveling everything together, the downside is that I will run out of leves very easily when I reach lvl 67+. So I am saving a lot of my leves at this point. However, I always keep the allowances below 90, so I don't waste the auto-refill each week. I do have 1 or 2 classes which are higher than others. This is due to either (1) I just want it to go 70 first, or (2) by chance, I just have a lot of mats for that class.

I know a handful of people who doesn't do things this way. But they have their own valid reasons. For instance, some wanna be able to make the highest level gear for sale first on the server. They believe there's good money there. So they're pouring everything into that one class asap. Is it a good approach? I dunno. Maybe? Maybe not?