With the recent nerfs to Zekvir, Tier? of Zekvir's Lair can farmed rather quickly and will reward players with 616 Hero-track gear from the Great Vault!
Delve Rewards Guide
Last week, several nerfs were made to Zekvir's Lair which includes lower boss health and damage along with a much easier time handling the add spawns throughout the fight. On Tier? difficulty, Zekvir has a total of 80M health making this a pretty easy boss to defeat with appropriate gear and item level.
Zekvir's Lair counts towards filling Great Vault slots with Tier ? rewarding the equivalent of a Tier 8 Delve. This is 616 item level gear on the Hero Track. In personal testing using a 600 item level character, Zekvir took rougly 2-3 minutes to defeat meaning a full Great Vault would take just over 20 minutes of farming.
This is an efficient way to fill Great Vault slots across your characters, especially if you are running low on Restored Coffer Keys or don't need rewards from Bountiful Delves.
The following build for Brann Bronzebeard is recommended when taking on Tier? of Zekvir's Lair. There is quite a lot of incoming damage in this fight and having the extra dispell is always convenient. The Curio choices also help with player survivability which can be useful for solo players.