The potion brewing system as always felt incomplete to me. All the potions are crafted using a single base, and the other base potions do nothing at all. I've always gotten the impression that they rushed the feature into the game before they were finished with it.
I don't mind it too much, I guess they could make harder to obtain new bases that make more powerful versions of the regular potions. If it was like that, just adding one new base would enable the ability to make long lasting level two potions and very short lasting level three potions. But I'm not suggesting the addition of a newer, stronger base.
No, he just means reduced fire rate or weaker shots, not magical slow gliding arrows.
Yes, dullness potions don't slow down time. They would just slow down the fire rate of skeletons. I suggested this because dullness wouldn't have much use in single player if it only slowed down mining speeds.
I've an idea as to what to do with the apparent issue of rubies not having much other purpose: Ruby tools and armor. Now, now, don't toss your rotten tomatoes just yet, they could make for a decent bridge between Iron and Diamond (The gap between them is relatively massive).
With the Wither affect potion why not have it so a wither has a 10% chance of dropping an item called a wither root that takes around a Minecraft year to grow therefore making it hard for someone to obtain the potion
That's stupid, nobody would ever obtain it. The Wither is too annoying to grind on just for a wither root and you need to have a serious addiction problem to farm it.