So, im not really a big fan of dung, but these two rewards really caught my eye. Now, after hearing about the bone crusher, im not totally sure its worth it anymore, but what about the herbicide? Is that worth getting the 34k tokens, or is it about as useful as the bonecrusher?

Neither will really revolutionize the way you train and I would really recommend prioritizing what you want from the tokens you gain, since they take such a long time to gather. They're nice, and they help your efficiency, but again 60k+ tokens is a huge investment if you're going for say, a chaotic rapier.

Neither is worth it for the xp. Herbicide may be useful for clearing herb drops while cannoning aberrants so you can see all the good herbs.