I hope you don't mind a random tangent regarding Hoodwink, but I figured it would be cool to discuss exactly how it works and the fact that it is not simply a beefed up Decoy. I will get to the answer to your question if you stick with me.
When this object is the target of an enemy controlled spell or attack, you may reveal Hoodwink: Gain 3 mana and then destroy Hoodwink. If Hoodwink is destroyed, even if hidden, you may place it back into your spellbook.
First thing to note is the reference to "this object." This is referring to the object that Hoodwink is attached to, and not Hoodwink itself. So, if someone tries to destroy the equipment that you've attached Hoodwink to, then you would reveal Hoodwink after the Cast Spell step, gain 3 mana, destroy Hoodwink, and put it back into your spellbook.
However, if someone casts a spell onto Hoodwink directly, you don't get any mana from it. You do get to put it back into your spellbook though if it is destroyed by said spell.
A really crappy thing to have happen, is to mess up and reveal Hoodwink at the wrong time. If you reveal it at any time other than when the object it is attached to is being targeted by an enemy Spell or Attack, then you do not gain the 3 mana and you do not destroy Hoodwink. It now just sits there face-up and laughing at you until someone chooses to destroy it.
Finally, Hoodwink does not have the Cantrip trait and can in fact be kept from going back into it's owner's spellbook. To do this, you must simply manage to counter it before it's spell cast is resolved.
So, if you used it to trigger an Arcane Ward, you would indeed lose it. This is because it's text doesn't get a chance to take effect since it never resolved. Similar to Decoy.
Moving on to the rest of your concern, [mwcard=MWSTX1CKE01]Armor Ward[/mwcard] would never require two crumbles. I'm guessing you actually meant to say Arcane Ward. The best way to get past Arcane Ward on a piece of equipment, in Arena, would be to cast Dissolve which targets the Mage instead of the Equipment. This bypasses the Arcane Ward trigger and results in the destruction of both the Equipment and the Arcane Ward.
Now, you can't use Dissolve in Academy though, which makes things significantly more difficult. There are actually very few things that target the equipment in Academy. These include Arcane Ward, Crumble, and Hoodwink.
Out of the three, using an Arcane Ward of your own would actually be the most efficient. It is a gamble though since if the Equipment had a Hoodwink on it instead of an Arcane Ward, then you've just given your opponent a Mana increase and put the very spell you feared onto their equipment, protecting it from your own Crumble. You do then have the option to reveal it without it's trigger, in which case it is destroyed and discarded per the rules on page 17 of the Academy Rule Book, but you've still lost two mana and your opponent has gained a pretty decent swing in Academy.
Casting a Crumble is a really crappy option because if it does get countered, you've used up your Full Action so that you can't follow it up with another Crumble right away. They will often be able to just put Arcane Ward back on, unless you wait till the very last action in a round before you gain initiative.
Hoodwink is only an option if you're a Wizard, and doesn't suffer any drawbacks other than you will be losing your one and only copy of the spell. This may be worth it on occasion.
