Gale did ask me to acquire the idol for him once, because he chose to reveal himself on night 1 after glitching out. He asked.
By his delivery, he knew it was an evil choice.
I don't think it's reasonable to assume the druids would part with it willingly. Proof? Gale thinks they wouldn't. Respond (in my memory) "that sounds like more trouble than it's worth" and he'll back down with "haha, yeah that would be stupid. Only brainstorming. There's artefacts everywhere".
You cannot convince me he wasn't /fishing/ to gauge your character. It was manipulative and machiavellain. I know machiavellain people, and what drives their behavior. Gale, however, has not the necessary broken and repurposed gears to be one proper, making the whole encounter slimy.
Gale is greedy. People have been saying his flaw is hybris, but I don't think so. It's not hybris that makes him do stupid things. It's greed. Greed, to possess all of Mystra's affection. Greed for power for the sake of power. Greed to /consume/.
His ego was never the problem. It's how far he's willing to bend his morals for his heart's desire. His greed will cause the artefact to gain in power... or doom his soul.
Pinning hybris on someone, I'd have to go with Astarion. That weasel thinks he's on the road to becoming invincible. Even Lae'Zel is foolish enough.
I do think our perspectives differ because of what we perceive Gale's fatal flaw to be, though. Greed can't exactly be misguided the way hybris is... nor does it go away with wisdom. Furthermore, greed would mean absorbing the artefact probably/wasn't/ an accident. He just didn't expect it to sap his power. Greed would mean he's still sticking to the plan of unlocking its full potential -- not seeking a cure.
Most of all... greed means he's evolving into something highly favored by Shar. Shar is not nice in bestowing favors. They do not end well for the target. That thing is a curse for anyone it comes in contact with. It may as well be Gale's desire to consume Mystra given physical shape.