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i dont think the alchemy mats are rarer, I think it's more that there's a lot more of them. Blacksmith has iron, clothing has jute - alchemy has i don't know how many. I haven't had a problem finding mats. Also keep in mind it takes more mats to craft an item then it does a potion.
I've found that leveling alchemy is actually very quick if you know want to do some research online first. "Experimenting" and making a potion that discovers multiple reagent attributes can give a lot of experience, especially in comparison to a craft like clothing.
As for finding the reagents, sometimes it's best to just run around and look. If that's just not doing it for you though, you can run in a circle where you've found multiple nodes. The nodes will always respawn over time with another alchemy reagent.