Act IV has been live on the Asia server now for approx 1.5hrs. Once completing the quest it unlocks the challenge "Awaken the Resurgent Cryo Regisvine". Already I have found this event to be extremely buggy. Here is what I have found.

Summary:

Once you start the challenge, you need to kill the monsters for Crimson Agate. Use these to destroy the ice shield around the Regisvine. Once the shield is destroyed then the boss will have a health bar and you can attack it as you would any other Regisvine.

During the fight it will AOE the area with a blizzard that does a lot of damage over time. Destroy the Seeds of Winter near the heaters for a shield.

During Co-Op, if the whole team dies, or you run out of time you will fail the challenge.

Bugs:

1. Co-Op Instant DeathIf you join a challenge that is already in progress there is a high chance that you will join whilst this AOE is happening or in line of fire of another one of it's attacks. This often causes instant death. You are given the revive option.You will respawn outside of the challenge and have to go to the glowing spot on the ground to join. This will cause a load screen and also give a chance for you to rejoin the challenge to instant death again.
2. Crimson Agate having no affect on Ice Shards/Ice ShieldMultiple games I have joined have not had the Crimson Agate work as intended to destroy the ice shield surrounding the boss. This causes time to dwindle away and can then cause a failed challenge as time runs out.
3. No Boss Health BarOnce destroying the shield around the boss, a health bar should appear at the top of your screen just like any other boss. I have encountered twice now where a health bar does not appear. The boss does not "stand up" like other Regisvines. Attacking the boss does nothing to engage or start it. In once instance 4-5 minutes passed before the boss was engaged. This can cause a failed challenge due to timer expiration.
4. Seeds of Winter disappearing or not producing shields.At times, destroying the seeds of winter does not generate AoE shields to protect from the blizzard. This then causes death resulting in point 1 when you try to rejoin the challenge.
5. Weak Spots not spawningThe weak spots on the Corrella and Roots do not spawn. This allows the timer to run down allowing for Challenge to fail due to timer expiration.from u/Yoha_Cl

These bugs make it extremely difficult or impossible to complete the challenge and get the achievements and currency for the event.

Is anyone else experiencing these bugs or any others? I am about to submit a CS ticket as it doesnt seem like this event is operating as intended.

Edit: Solution?

As per u/sharazarade*'s comment:*

"You actually get weaker slimes with no shields and no flower type enemies in single player so unless you get a decent team AND no bugs, co-op just isn't worth it unless you're lacking in pyro power. "

Single Player Mode seems to be the best quick fix for this.

TL;DR The newest Co-Op Challenge is buggy as hell and near impossible to complete at times