A handful of mobs, including Obnoxious Fiend on Heroic Atramedes, generate massive warning spam; multiple warnings for a single cast. I don't know why yet, but it really needs to be fixed immediately as it's extremely annoying. My best guess is the mobs are actually bugged, and repeatedly generate "immune to interrupts" vs. "can now be interrupted" events. But that's a guess, and even if it is a Blizzard bug InterruptHelper really needs to recognize it and work around it.
Workaround: It's only certain mobs, so just disable tracking on those mobs or spells. InterruptHelper will work for everything else, and you can reenable this as soon as the bug is fixed.