@Arkdeniz: I am sorry that this makes you uncomfortable, but your interpretation is indeed wrong. It's even wrong for Academy, as far as I can see. I am less well versed on Academy rules, but as far as I can tell there is no rule like you imagine that limits defenses to only happening during the Avoid Attack step. Even if there was, the text on the card always overrides general rules and both Jade Gremlin and Symbiotic Orb say that they happen "when attacked". Which means at the end of the Declare Attack step in both Academy and in Arena. If it was meant to happen during the Avoid Attack step, then it would say that.
It hasn't been my interpretation in practice - my group has played it differently again (see above). But topics like this always make me get the rulebooks out for a closer read and get me thinking, which is always fun.
But on reflection I do not agree with your last sentence. ("If it was meant to happen during the Avoid Attack step, then it would say that.")
I would agree with you if we were talking about Arena cards. Block, for instance, clearly states that its Defense power takes effect in the Avoid Attack step. I cannot find any Arena card that does not state the specific steps in which its effect is used.
(BTW: If you can find any Arena cards that have a flat statement of "when this creature is attacked" that does not go on to state a specific step for its effect then you can reveal that card now and not bother reading further - your point will be made.)
Only Academy cards have the phraseology "when attacked" without adding any specificity. This makes me suspect something is up with that ruleset.
Academy cards are intended to crossover between the two rulesets. And because Academy has a "Defense Step" as its equivalent to "Avoid Attack" (Oh I wish they had kept the same terminology!), the card could not give more details lest they confuse the player base. Say "in the Defense Step" and confuse Arena players; say "in the Avoid Attack step" and confuse Academy players. Say "in the Defense Step or in the Avoid Attack Step" and confuse both groups! So the cards say nothing at all, which opens it up for interpretation.***
And I don't think your interpretation is necessarily right.
If you look at it a little closer, you find that "When attacked" does not always and cleanly mean "the end of the Declare Attack step" as you say it does. The aforementioned Block, for instance, reads "when this creature is attacked, you must reveal Block during the Avoid Attack step." If you are right about the meaning of "when attacked", then Block's text will translate as "at the end of the Declare Attack step, you must reveal Block during the Avoid Attack step", which is clearly unworkable gibberish.
So for Block, and other Arena cards like it, the "when this creature is attacked" phrase must refer to the continuum that is the whole attack sequence, (and is amended by subsequent detail).
I can't possibly conceive that the intention is different for Academy and its cards, but Academy repeatedly fails to include the necessary detail.
Finally, I go back to the word Defense. Unless you can point me at chapter and verse that says Defenses can occur at different times in the attack sequence, all I see in the rulebooks, the codex and supplements is that Defenses (in both rulesets) are exclusively discussed in terms of their use in the Avoid Attack/Defense steps of the two games.
Which is why I have to conclude that when Academy cards refer to Defense, then the effect takes place in the Avoid Attack step.
*** Academy has the same problem for cards whose effect cancels attacks (rather than avoids them through Defenses). Compare Academy's Repulsion Field ("When this creature is attacked you must reveal Repulsion Field. Cancel the attack.") with Arena's Helm of Fear ("whenever this mage is attacked, at the beginning of the Declare Attack step... That attack is cancelled").
Whether I convince you or not on all of this, I think Academy's designers missed a trick when they decided to use different terminology than Arena's for steps in the attack sequence, and a second trick when they did not include on the cards specifics on the step for each effect, as Arena cards have. I would urge greater care in future.