Confuse resistant is not confuse-proof.
I've managed to confuse Scirocco during an STF, it was funny as hell to see him sic his dust devils on Ghost Widow. Granted that lead the Tank to lose aggro and nearly cause a team wipe. <.< This was back on Legacy before Incarnate system was released.
Many support enemy's pets are untargetable, but if you confuse the support enemy first, their summoned pets will be confused. My personal favourite are Rikti Comm Officers, which will spawn confused portals, that will then spawn an army of confused Rikti. But Longbow Engineers and their turrets or shield generators, Arachnos and their Arachnobot Disruptors, and pretty much anything else that summons pets. Likewise buffing enemies will buff you and your team while confused.