We have crunched some numbers on our guild progress database to calculate the best time for guilds to move on to Jin'rokh in the Throne of Thunder. The chart below shows the progression of guilds before they go on to kill the first boss in the Throne of Thunder. We have filtered out the advanced guilds by only looking at those that killed Jin'rokh on normal mode last week.
As you can see, guilds with kills as early as Blade Lord are moving on to Jin'rokh and having success. Our stats also show that guilds are killing him with an average ilevel of 491. So if your guild can already kill Garalon or Wind Lord Mel'jarak then consider going and grabbing some ilevel 522 gear off Jin'rokh in the Throne of Thunder.