For beginner groups using Saxhleel Champion is great because you can use either Colossus as a Necro or Barrier as any other class and boost group survival by a huge amount but at the same time still provide the Warhorn Major Force buff to the group at the same time.
I’ve listed Worm as the second set because it’s easy to manage but you can use other sets if you are comfortable using them.
In 99% of groups you’ll separate the twins bosses – in that case you’ll want to have Powerful Assault on both groups and Encratis on both bosses. You also need Elemental Catalyst on both bosses – because the damage they cause is so small its generally not a problem to use PA/EC here.
If you have a hard time surviving then switch PA to the Weapons/Jewellery and use Saxhleel Champion.