Having recently moved from dual boxing SWTOR to quad-boxing, there are definitely advantages for either setup but I love the quad-boxing so much more. Once I got past the initial setup (dual-boxing in swtor is seriously easier to setup than 3/4 accounts) the game has been a blast for multiboxing, it's just not quite as easy to setup as it is with WoW (quint-boxed WoW).

The camera-viewpoint of the slaves will always be an issue it seems so you're not doing anything incorrectly there. Mouse click AOE's will always be a pain as a result.

Like pox67 mentioned, leveraging the click & release is very important and which commands in what order and how to separate which into steps. For example, I use a dedicated key for assist: "press" fires step 1 which is defined as target the current lead character slot and the "release" fires step 2 which issues the assist command. Since these are both in-game keyboard commands it's been my experience to have them as two separate steps in your key map and it works very well. Then I use whats nicknamed the "popsicle" setup which is like a pseudo-macro setup of like a DPS key that fires off the next available attack ability in the order you defined.

Also, I highly recommend looking into setting up ISBoxer's "click bars" to manage CC and heals which moves the use of buttons on your device to a virtual buttons in-game overlay. Other boxers commonly use this method so there are ample examples out there but I can post my current example later when I'm back at home if you're interested.