Adding monster pack spawns as random events

An idea I had: I think the multiple monster waves with several bosses at the same time at shrines and near rifts are some of the more interesting fights in the game, but they are one time only.

How about adding these same events with a random occurrence rate?
They could be guarding a chest like a Nemesis trove that is unlocked once you’ve beaten every monster, which gives the player another layer of incentive to do them besides the drops and thrill from the fight itself.

No one interested?

I think that little random events, such as running into a Trove or a monster pack encounter like this would be good, since it would be something (slightly) different to break the monotony of your preset runs.