Hello, unsure if that behavior is intended but the targeting for effigy of combustion in combination with the hellfire node that makes the infernal shade ground targeted also causes the triggered infernal shade to target nothing randomly placing it somewhere in the screen or sometimes off screen. I would have expected it to either be placed where the zombie died or under the closest enemy but that is not the case.
Edit: after further testing the targetting issue appear to be unrelated to hellfire. I unspecced hell fire and then I noticed that instead of infernal shade spawning 100% of the time when the zombie dies it would only appear around 50% of the time. I suspected it might be due to it spawning randomly and having nothing to attach to so i specced lingering flames and now the shades appear randomly but they do appear 100% of the time.