Alright, clearly two words wasn't enough.
This is about the second half of the card, where Mind Shield does something no other card can do: it lets you reveal Mind Shield during the revealing of another enchantment. Normally, you can't reveal an enchantment during revealing an enchantment, because the steps to revealing an enchantment don't give you a chance to react (MtG would say they don't pass priority). But suppose I use Mind Shield to destroy [mwcard=MW1E30]Pacify[/mwcard] while you're revealing it. If I have some other effect that triggers when you reveal your Pacify I'll get to do that, too, if I can use a delayed trigger, even though the Pacify was canceled.
If you really want to make it hideous, you can do all this during an attack by a Passage Attack wall. Imagine a world where [mwcard=FWE01]Charm[/mwcard] was "Psychic, Curse" instead of "Psychic, Control". I walk my creature through a Wall of Fire, and during that creature's movement you reveal your Charm on it, to get benefit from Smouldering Curse. I then reveal Mind Shield while you're revealing the Charm, during the passage attack, while the creature is moving. That's a lot of things happening simultaneously, all of them potentially triggering. If I can stack and rearrange the effects of those triggers I'm going to be able to do some very weird things.
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Consider the MtG model of triggered effects. Every triggered effect is a grenade. After the trigger, grenades wait on the stack until they are processed later, last in first out, regardless of what has happened to the source. For example, in MtG, if an upkeep effect would destroy a Ghoul Rot, and the Ghoul Rot would do 2 damage, both effects would go on the stack and then would be resolved independently, and both would happen regardless of the order they resolved.
Contrast this to the much better Mage Wars system where triggered effects are much more like hitscan weapons. The trigger is pulled and the effect occurs before any other triggers can be pulled. If there's a conflict between two triggers, they're processed by priority depending on who controls the creature (or in some cases, initiative). But a whole trigger -> effect sequence is resolved sequentially, with each trigger followed by its effect before moving on to the next trigger. If an upkeep effect would destroy a Ghoul Rot, the creature's controller can destroy the Ghoul Rot and then the Ghoul Rot does nothing because it's gone.
If we try to import MtG's rule that all sources are potentially triggered regardless of their own destruction we're breaking the Trigger, Effect / Trigger, Effect / Trigger, Effect sequence. Instead we would have, "Trigger, Trigger, Trigger, Effect, Effect, Effect." This is bad, because it means we have to import a whole bunch of other MtG rules that conflict with extant (and superior) Mage Wars rules. We need a Stack, and triggers need to "see" their source's destruction, and probably a few other things like APNAP which I'm really too tired to figure out right now.
Like Zuberi said, in Mage wars, Magebane's effect needs to resolve adjacent to its trigger. It either needs to resolve before the spell resolves and it's destroyed (which can't happen because the spell didn't resolve yet) or after it's destroyed (which can't happen either, because destroyed things don't trigger).
The exception, as Shad0w noted, is that sometimes things trigger when the source are destroyed. This is a special template used for Cantrip, Rise Again, Mind Control, etc. If it is important that Magebane trigger when it's dispelled by a spell, the way Mage Wars rules would do that is to add an additional erratum sentence that says, "If Magebane is destroyed by a spell cast by this creature, this creature receives one direct damage."
In that situation, in order to maintain the Trigger, Effect, Trigger, Effect, Trigger, Effect pattern the prior effect is allowed to finish resolving (Magebane is destroyed) and then the special "on destruction" trigger occurs, and is placed in order by priority (again, determined by creature control or Initiative). Triggers continue to be processed, as normal, each with their subsequent effect. When that "on destruction" trigger comes up for resolution both the trigger and the effect are independent of the original source because the trigger explicitly says that it happens after the source is destroyed.
Otherwise the assumption is always that destroying the source of an effect prevents it from triggering, and that the trigger will be tested for legality at the time the source causes the effect, and that one of the preconditions for that effect is that the source exists. This is one of the best mechanical differences Mage Wars has from MtG, and it avoids so many counter-intuitive situations, and is responsible for the much higher feeling of verisimilitude Mage Wars has.
