I finally got to 10/10 10/10 sigil jiggers today, and was able to move on to the next step in the legendary quest chain, which is killing the Sha in Terrace of the Endless Spring and looting a chimera thingo off him.
This bit is where the tip comes in…
As I had already done Terrace LFR this week, I thought I would test if you could still loot the quest item if you were saved to the instance loot-wise.
The short answer is that it was a SUCCESS – you can INDEED do Terrace for a 2nd time in the same lockout and loot the Sha for the quest item. The ensuing questline is awesome, to say the least (spoiler alert!)…
Gimme some love – and a gem!
I now have my drool-worthy Sha-Touched gem – now all I need is the weapon I can socket it into!
I hope this tip helps!
untamedhellcat 
I feel like Wrathion will be getting all this death and destruction in his name to make himself more powerful, and then do something nasty. Giving away epic gems? Only if he gets something far better.
Grats Gen.