As you may have encountered the mini-bosses. They are pathetic though. they don't pose ANY threat if you play it safe. What I am suggestion is to make them actually pose a threat. Firstly, they need to have some GOOD life.at least 350% of the sectors regular mobs. AND they could have a chance to generate with some sort of damage reduction (percentage or flat value) Secondly, they are easily trapped. Maybe make them break 1 layer of blocks around them when they are tracking you AND cant seem to get to you. Lastly, There should be a cap of mini-bosses on any planet a given time. I am thinking maybe 2-5 depending on the planet. They should also stick around until they are killed (If they dont already). If you have an opinion feel free to reply even if you didn't like it. Just say why and I may adjust it so you are more content with this suggestion.