Now that my main character is level 50 and fairly well geared, I'm spending some more time exploring other classes and their class stories. The problem is that I have already done all of the side quests three times now! So although I am enjoying the main class story lines, which are fresh and new for each class, I'm finding myself not wanting to repeat the hundreds of side missions yet again.
To avoid them I'm playing avatars at the same time and taking full advantage of rested XP. As you can see in the screenshot here, I have three quarters of a bar available in rested XP. The green outline indicates how much double experience I will get. The double experience applies to all NPC kills but does not include the actual experience you get from the quests or from space. With three quarters of a bar of rested experience I will be getting double XP for all my kills for up to three levels. This is allowing me to skip a lot of the side quests on most of the planets for all my alt avatars.
To get rested experience, all you need to do is log out in a cantina or on your ship. Rested experience will cap out at a full bar.
Other things I'm doing to avoid side missions are the daily space missions, which are quick and profitable, and also PvP. Spending all my warzone commendations on gear for for my alt characters and their companions makes up for the loot that I missed out on getting by choosing to not do side missions.