Any time (well, any time I'm not in a Raid... that pretty much rules out Tuesday nights). I did the raid on Hard on the weekend with my Warlock... and finally got the raid helmet! My Warlock is now lvl 30! (well will be as soon as I complete a few bounties to unlock the last upgrade or 2)... my Titan and Hunter both need one more piece for lvl 30, gloves and boots respectively if I remember right.
I also got Atheon's Epilogue and the Vex Mythoclast at last!!
Still not done the raid