keep in mind that this game is being developed by a very small team. They can't do everything perfectly, especially while developing their next title. That's why there are generous players like Papa Lazarou who put their time into making improvements for this game. Look for their mods and thank them for doing this instead of *****ing.
Tutorial? What's a tutorial? Oh, you mean that stupid little minigame that you can find in almost every title and that teaches you next to nothing about the actual gameplay? Joking aside, as someone who makes a point of learning the game through playing it, I can tell you that you're complaining too much. The tutorial doesn't mention speed bonuses? well, unless you're blind, the first time you play the game you'll see they're there since your damage reports would be on. The tutorial mentions nothing about chambering? Again, unless you're blind, you'll learn about them by seeing them happen.
Arena setup:
the setup historically was really up to the person(s) organizing the event. The Romans did send people naked against lions. And they did gather cripples and beggars from the streets and tie them up in the circus just so the emperor can crack their defenseless skulls. So in this line, I imagine, the devs decided to force players to use more than one weapon type (for their own good). Considering there wasn't such a thing as a dedicated arena building in the Middle Ages as there is in Calradia, we can safely assume that the deed of giving random weapons to participants is a purely Calradian custom

What I personally hate about the arena (and Warband in general) is how the AI likes to always gangbang the player. I've literally had the situation where all six NPCs dropped in the arena along with me went after me and nobody else. So I tend to stay out of the arena with early game chars, which kinda brakes the point of the arena in the first place.
Let me reiterate - have you fought in armor? From what I see you seem to like to complain more than you like learning. And make no mistake - anyone here that has played the game longer than you has certainly had to deal with much more frustration that you.