Present GO batch has one stage with enemy that has rage bar, so it is pretty bad. For next GO batch stages 3-5 have enemies with rage bar. Will stun punishers be useful there ? Doubt it, but we'll see.
That's half of AQs though ? Okay, that's only stage 2, so it's not terribly useful indeed.
Hold on, define this "just about all content", because aside from Light present Ragnarok raids have stun phase 'pretty early'. Raid events also very often have stun phase before end of fight.
Also for me "niche use" means that something is less than optimal in most cases, but in some it may be the best option.