Guild Wars 2

If a warrior has this weapon equipped in his offhand slot, does the sparkly aura/footprint effect still appear?

nope, this goes for all legendary weapons. only those in your main hand will show the footprints.

It’s actually only if you have another legendary in the mainhand that also has footprints. If your mainhand doesn’t have a legendary with footprints then the moot footprints will show even if on the offhand.