If you haven't done them... Mustafar is THE best answer to the Quest xp thing. Since your higher CL you really don't have any quest restrictions (A CL 20 for example can no longer group to do a CL 60 mission if I understand my patch notes right).
Mustafar aside your looking at doing any of the ground quests you have left on Kashyyyk. This looks to be what their tooling up to be around the CL 40-80 planet while Mustafar is the CL 80+ planet. Just with huge gaps in CL not accounted for forcing some players to grind vast ammounts of xp in places. The NK-Necrosis is perhaps the highest repeatable mission there at 98k reward. The rest really seems geared more for a 30-50ish CL with a few group 70-80 quests (Blackscale/NK/Ryatt).
The Legacy quest starts in Mos Eisley. This multi-arc quest takes you all over the place and can probably generate at least one to two CL by the end of it for a CL 80 toon. You start at Vourk (sp might be off) just to your left as you leave the ME Starport. If it is buggy... you can pick it up with either Theta (again, sp?), just around corner if you go straight to where the Entertainer trainer used to be and turn to your left (she's dressed like Obi-wan). If you still can't get the Legacy Quest started... hit up the Mayor and it should kick in. You'll have to do some tasks around Eisley, end up at Watto's, do the 'new' Jabba's theme park, wind up on Naboo... and your adventure keeps going for awhile.
Alternatively, the other options for right now are...
Grind:
Space: It's counted the same as ground xp at least till dbl xp is over and I believe is also dbl xp.
Repeatable missions: The Tulrus hunting quest is a favorite of mine on Musty.
Do Corvette missions: You can probably get about, roughly, 1/12th of a bar each time you go. If you do them for loot runs/xp/badges.... the time really does equal out for your total gain. Goes faster in a group obviously.
Your last option... Super Marios Bros. 1UP Life Day Orbs!