I use the i/o plugin on individual audio tracks all the time to pass recorded audio through my analog EQ's and compressors.
For example, just yesterday I was using my Kush Electra to EQ a snare drum track.
On the snare track I insert the i/o plugin, configure the plugin according to which output and input I'm using, turn on input monitoring for the snare track, then ping the track.
Works every time.
Mike