Finding the right second class

[Bixby]

Don't bother with alts just for Myth Stones. The weekly cap will be lifted in a few weeks anyway, and you aren't high level enough yet for it to be worth the effort.

But at the same time, we'll be getting a new kind of tome that will almost certainly have a weekly cap.

Honestly, it's just a matter of what you enjoy more and what your priorities are. What's more annoying, weekly lockouts or having to repeat content/leveling? If you enjoy having an alt, have an alt. If you don't, don't. It's not a definitively good or bad decision either way.