I started tripple boxing some shammies this week (Yes I upgraded to 3 accounts, go me!). Here are a few things I did to get myself set up, including key bindings:

I unbound the a, s, d, w, keys for movement on all my alts. If i need them all to turn left, because the mob came at me from the side while looting a corpse or something, I use the arrow keys. I use asdw a lot as well as my mouse for moving my main around. I am on a laptop, so I bound autorun to ` on all of my toons but put that on the 'do not pass' list. I keep the main action bar, 1, 2 3... 9,0.-.= as defaulted. The left action bar is Shift+1, 2, 3.. ect. The lower right action bar is ctrl+1, 2, 3, ect.. and then I have the right action bar as alt+1,2,3 ect. I am not using the second right action bar yet, since my shammies are low level. Using the same settup for 3 mages I'm running as well.

I swiched from /assist using no focus to utilizing focus for everything now that I'm tripple boxing, makes life easier. I'm sure that'd help for your 4 boxing.