New deadly minibosses have started spawning in Tier 8 delves and they are so difficult, you probably just want to skip them.
In yesterday's hotfix notes, Blizzard announced that new mobs would be appearing in Tier 8 delves. These were previously on Tier 9+, but have now entered Tier 8 as well. Some of them are so difficult, you're better off just skipping past them.
There is one of these minibosses in every Delve that is level 8+.
Tala and Velo have around 31.5M health each and have a lot of different abilities.
Tala is a caster and spams Web Blast at a baseline, hitting for 1.5M per cast. They also cast:
Velo uses melee attacks using Void Slice to deal ~430k damage and applying a magic debuff that absorbs ~500k healing. They also cast:
Essentially, because of the shield, players are effectively forced into killing Velo first which likely gives them threat. This means that they get a nice healing absorb from Void Slice and then have to decide between kicking two spells, one of which does 3M damage up front, and the other which deals a total of 6M damage over 12 seconds (if no poison dispel). This is a lot of health and I highly suggest not even bothering to kill these minibosses.
Venombite and Kas'dru are another duo miniboss. Venombite has 23.1M health and Kas'dru has 34.7M health.
The main thing to note is the Kas'dru cannot be stunned or interrupted via Mounted Defense until Venombite dies which is unfortunate, because of his abilities: