I have completed all of the 8 guardians now, They are a bit too hard right now and I want to polish them up to make the fights more fair. In total some of the starter bosses are more hard. 

As well as there is a new upgrade that resets your guns level in exchange for a perm upgrade to damage that's stackable. 

As well as this your exp, and lvl and upgrades are saved when you die instead of only when you complete a boss fight.