Is there a visable difference between a level 2 herb balance and a level 0 (normal) herb balance?

Yes.

Along the same lines:

When harvesting, is your speed determined by your balance recovery, or is there a special "harvesting balance"? What I mean is: would a faeling harvest fater than a Tae'Dae, disregarding whether one has gloves or not?

It's effected by regular balance, so balance-bonus races make better herbalists.

(Filthy faelings with gloves. >< )

But it isn't affected by negative balance, or else I wouldn't be harvesting at about 3 seconds as a tae'dae...right?

As faeling with gloves my bal recover seems to be just below 1 second.

PS: Replanting doesn't seem affected by it though, or if it is, not by much. A shame really. I'm all for lightning speed replanting balance plz!

I guess when I say "visible" I mean does it have a noticeable effect on combat?

Does for me... eating herbs that much faster is always a plus, right?

If there's an herb cure and some other cure, I go with the herb cure 99% of the time. It makes a difference.