% for getting nether star shard is way too high. 1% is high, not comparing to 15%. If you can make a config file for your mod would be awesome.

By the way, how are you farming the end stone?

Beeing in the End? I'm just digging to get quite a number of nether stars, it's too simple compared to farming Withers. You can also change end stone to something harder to get and non-replaceable, but I have no idea which item from End dimension would fit.

So, here is my thinking to address this:

To obtain a Nether Star, one needs to kill wither skeletons and get 3 skulls, then summon and kill a wither

How about a recipe that crafts 9 wither skeleton skulls into a Star? No wither fight (which was my intent) but player still needs to get 9 skulls per star. What do you think?

For now, I am closing because there is an option to adjust the drop rates of Nether stars in the config. I may look at other options in the future.