There is 4 Loading Screens before game loads
1. When Launching Game
2. when entering password
3. When Loading to character select screen
4. After selecting chararcter
Are these necessary? it should load after you select character no?
Then you can select and then ALT-TAB out for some Firefox action while it loads once not 4 times
When launching the game: The game is initializing all the stuff it needs to run.
When entering a password: The game needs to authenticate that the login information is correct, which requires talking to the server both to verify that and to verify that the device is trusted. (If it's not, then you get the confirmation email).
When loading to character select screen: The game has to take all the character data associated with the account and load those characters, and I believe this is where addons get loaded if on PC.
When selecting a character: Well, you need to get into the game world somehow.
In short, yeah, it is necessary. Caching saves some time, but you're going to have to wait for user input at several points in the process.