Trang-Oul's Wing question

[Little Faith]

There is nothing wrong with the bonus. It will work on any attack originating from you. (But will have no effect on your minions, unless it is the minions who are wearing the -enemy resistance gear).

I guess the build guides you mention depends on the very rare Death's Web for the -enemy resistance. For those of less fortune three piece Trang's with the Wing is highly recommended.