When multiple sorcerers are casting mages wrath on a single target, IF those casts are synchronized (meaning multiple sorcs casting at the same time), the bonus execute damage proc will ONLY fire off for one of the casting sorcerers.

Specifically, the "If the enemy falls to or below 20% health within 4 seconds, an explosion deals an additional x shock damage to them and y shock damage to other enemies near by.'

This execute 'proc' does work on the endless fury morph of mages fury and we did not test the un morphed version.

Steps to reproduce:

Have at least 3 sorcs in a group (3 because its easier to see the sync with 3 or more than just 2)
we tested on the possessed mantikora in normal sanctum ophidia
damage boss to below 20% health
have all the sorcs start casting mages wrath
it will be seen that on casts that hit the manti at the same time, only one of the sorcs will receive the bonus execute damage and the rest will merely see the base damage of the skill

When we followed the same steps as above, using endless fury, all sorcs always saw the bonus damage numbers on their screen.

This is on PS4 NA, so no addons or anything to confuse the testing.