The #CityOfHeroes Homecoming servers have enabled Double XP until at least Tuesday. This is additive with the START vendor's Double XP buff, so if you have that you'll be earning 3x XP.
Also keep in mind that the mobs that come out of doors while Trick or Treating are worth 4x the normal mob XP (versus those in a fire farm, for example). So now is a great time to get some levels on your toons!
(Zombie invasion mobs are worth 1/4 XP, so are not worth farming unless you want badges.)
You could also use the Trick or Treat event, or the Map server event in early April, to quickly get your character to level 50 and completely deck them out with enhancement sets. Then you could go back and play through all the missions in the Ouroboros flashback system. If you pick an AT that solos we'll, you can go through them all at your own pace. I've never found a group willing to wait while I read mission text, even if they say they will. They always enter the mission and start clearing it before I've finished reading. Soloing in Ouro lets me read the mission brief and experience the entire arc in full.
Sapphire
Lavaflow