Raid Progression

Progression in Rain of Fear is pretty straightforward. For starters all raids require the person requesting to complete the zone's partisan tasks and the first mission, but attending only requires previous raid flags. With group stuff done the first three raids are available:

With those three completed the final Tier 1 raid is unlocked: Eastern Wastes - Zeixshi-Kar's Shard.

Defeating all four Tier 1 raids unlocks five Tier 2 raids:

Velishan's Revenge is not required for progression. Completing the other four Tier 2 raids unlocks the Valley of King Xorbb instance with three events in it. The Xorbb raid instance does NOT require the Tier 1 raids so there is no need to go back for flags.

Defeating the three events in the Xorbb instance unlocks the first Tier 3 raid: Chelsith Reborn: Champions of the People. The other Tier 2 raids are no longer required. Defeating Chelsith (and Xorbb) unlocks the other Tier 3 raid Plane of Shadow: Dispelling the Shadows.

Having the flags for both Tier 3 raids unlocks the first Tier 4 instance: Heart of Fear: Glimpse, the Unseen. The instance contains 3 mini-raid targets which are not required for progression. With both Tier 3 raid flags and Glimpse on lockout you can request Heart of Fear: Memories of the Faceless. With both Tier 3 raid flags and both Glimpse and Memories on lockout you can request the last raid Heart of Fear: An End to Fear.

Once you are at end game grind any new recruits will only need the two Tier 3 raids as backflags to be fully flagged for Heart of Fear raids.

The Temple of Veeshan instance has no prerequisites for requesting or attending nor is it required for any later raids. It is a stand alone collection of Tier 1 raids with Vulak being Tier 2.