After 3.10.0e where some of the Delirium monsters received a 30-40-50% damage reduction to some of their abilities we are no longer getting one-shot by Shaper-like white mobs in T12. If you had decently built character with enough layers of defense you could survive most situations if you played with caution before these changes but now it is much easier.
The league mechanic also received a ton of extra rewards depending on your depth in the Delirium encounter. You are now able to receive multiple types of reward, each of which is stacking as you proceed to kill monsters. The mechanic now also has a much better interaction with past league content, like Incursion for example. The “End Delirium” button is now also bindable. Although this is definitely a quality of life change, it is not that necessary anymore to end your Delirium if you are not cought-up in a sticky situation.