No it's not. Macros are evaluated left to right. Your macro says "if holding a modifier and in form 1 -or- holding a modifier -or- in form3, then cast Rend. Else cast Piercing Howl."
Mine says "if holding a modifier and in form 1 cast Rend, else if holding a modifier cast Piercing Howl, else if in form 3 cast Pummel, else cast Thunder Clap."
This is a good site for how macros work:
http://www.macroexplain.com/