Rolling for Amakusa Shirou/Gorgon worth it?

Amakusa's NP is desirable because it clears buffs off of every enemy before it deals damage, and I think every other form of buff cleanse only target one enemy. He's pretty useful in most challenge content because of this unique property. Gorgon doesn't seem to have anything like that so I'm inclined to agree with your assessment, but I could be overlooking something.

Amakusa is way more useful for two reasons:
1. Virtue of being a 5-star servant.
2. He clears the enemy party of their buffs before inflicting damage on his NP. This will not be necessary for about 90% of the content in the game but is insanely useful for some of the harder content that we see in Nerofest and Salomon.

In certain situations, Amakusa is literally the best servant in the game to use since he is the only servant with an AOE buff clear (eg challenge quests and other hard content where enemies stack buffs) but otherwise he is only "good" by virtue of being a ruler, meaning he isn't really that good. Basically, he has a very specific purpose, and whenever you do need him you'll be thanking the gacha for giving him to you, but he isn't that great for everyday situations.

Gorgon is actually pretty good, her NP has a party NP charge tied to it, and being AOE won't be that much of a hindrance once break bars come in, which won't be too far off. The only thing against her imo is that Hessian Lobo is also an AOE avenger and is arguably better.

If you are basing your rolling on their gameplay value, just save for Merlin like everyone else.

Long story short, Amakusa is better, he's one of the best 5*s of the game for hard content.

Gorgon is gud but consider rolling for Komaeda as your AoE Avenger if you like him since he will dethrone Gilgamesh as the best offensive unit of the game (long term). If you don't like him, pick dat snek