OP:

I have found that 80% of my multiboxing time is dedicated to ISBoxer setup tweaking and 20% actually playing the game. I cannot count the hours and hours I have spent trying different things to make macros work and/or fail.

Targeting the target dummies for about 3 - 5 minutes of straight DPS is a good suggestion. Then review the damage log and trace back what is and isn't working.

Lastly, if you are struggling with macros and/or the step macros feel free to post your macros so we can take a look to see what may be going wrong for you.