The 1% is just an estimate- After using the log (which generates a herb) like 5 times every combat, for an estimated 20 combats (5-ish combats per room, 2 rooms per zone, I got the log at the start of zone 2) I went goblin after about 15-ish combats.
I have no screenshot, so you'll have to try this out for yourself. Keep on generating herbs, and eventually you are bound to go goblin. This is the only way I was able to beat the boss.