Saving this here.
I'm not a fan of glass casket and witching well in the slightest, I'm not particularly convinced that flavor should be a relevant factor on whenever red or black gets to destroy a permanent or is powerless to stop it. Plus I feel that "I want to run shatter because I need to destroy equips, vehicles, artifact creatures, colorless silver bullets coming from the sideboard or permanents with a strong tap ability" is more logical than "I want to run shatter to blow up things equipments, vehicles and random stuff that they wanted to have artifact flavor or they wanted to be weak to shatter and not mire in misery for play design concerns."
Even if they want an artifact matter block, it would be more memorable if the artifacts behaved differently from enchantments, imho.
(Ps. I'd also have loved if bolas citadel was an artifact enchantment, but whatever.)
I can see a complaint about glass casket. Seems like they could have done something to make it less direct comparison to oblivion ring type enchantments. Like maybe you tap it, the creature goes into exile while it’s tapped and it stays tapped unless you pay some (high) amount of mana to untap it. Something to make it a little different. Doesn’t really bother me cause I’ll take the flavor win, but I can see a complaint at least.
Witching well I don’t see the complaint. We’ve had artifacts you sac to draw cards before. We had
Implement of Examination in kaladesh that did basically the same thing (well costs 1 more but gives scry)
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X/X? Even the green x/x creatures cost at least 1 extra 
. Seems crazy it can go in any color and be as big 1 for 1 as your mana. 
