I am currently thinking “yes” as the rules text of a card is taken one sentence at a time, so the enchantment should already be destroyed by the time the lifegain would occur, correct?
You are correct. Since the steps are performed in order, and the enchantment is removed from the first instruction, it is no longer around to stop the second instruction.
Note that this is due to the "destroy" keyword action immediately removing the permanent from the battlefield. (Same for "exile", "sacrifice", or returning the permanent to its owner's hand.) The answer is different in the case of a damage+life gain effect (such as Lightning Helix) killing a creature preventing life gain (such as Rampaging Ferocidon). A creature marked with lethal damage isn't removed from the battlefield until state-based actions are checked, which is after the spell attempts to gain you life.
The same would be true for an effect which reduces a creature's toughness to 0 and gains life, like Moment of Craving on a Rampaging Ferocidon that had already gotten -1/-1 from another source.
I am currently thinking “yes” as the rules text of a card is taken one sentence at a time, so the enchantment should already be destroyed by the time the lifegain would occur, correct?
Please let me know if/how I am wrong.
Fixed tags
Invoke the Divine
You are correct. Since the steps are performed in order, and the enchantment is removed from the first instruction, it is no longer around to stop the second instruction.
The same would be true for an effect which reduces a creature's toughness to 0 and gains life, like Moment of Craving on a Rampaging Ferocidon that had already gotten -1/-1 from another source.
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)