What the previous user said, it has to be movement, at least for melee characters. Movement with melee is what really gives a bot away almost always, at least for me. This is just from simple observation in bgs, i have never tested out any bots in arena, and i'm thinking only thing that would even remotely work is maybe a healer class.
I played at decent arena brackets around 2.2k. I would like to tell you that it is possible to make a bot like this but requries much skill and time. A bot is a bot. It does not think. So my guess would be the bot would have to respond to when a certain class does a certain move. The circumstances of different chains of moves that players can use is many. It is possible but probably not going to happen.
I would love to see this happen, but as stated above there are so many things going on in Arenas that are class and spec dependant that it would take a huge amount of logic in the CC to even hope to get a decent rating. About the only thing I can see that would work decent atm would be if you had a well geared healer and you hand played your DPS class. I actually tried to Arena with my Pally using HB the other day, he was very easily confused with people moving around too fast and constantly getting confused and switching targets, after a couple games of that I just played by hand.
I tried combat bot(no movement) and resto shaman. He did heal better but would try to cast when i am kiting which basically made me die. First arena bot would have to be something that simply helps the player react to situations. Like instant trinket as soon as CC is detected. Auto focus interrupt casters and dispel. Combat bot basically does this now and I am sure enh shaman running combat bot would get much better results. I think focusing on getting bot movement right is too costly at this point. A player can control movement all we need to work on is making bot be able to respond to situations without getting confused. Arena bot that is geared will be able to handle sub 1000 rating arena even at this point.
How can you code an arena bot when there is so much random factors ?... btw, what's the point in botting in arena ? leveling, farming (gather, heroic, pvp stuffing) is boring, but arena !!
I don't think we will have an afkable arena bot in a long time. So if we do get an arena bot it would be something that gives you and advantage. Something that macroes can not do currently. I would love for a macro that would cast dps sequence unless target is casting at which point it would cast an interrupt. This functionality is not in blizzard's macros but the bot can do this even now. Many such prohibited conditionals can be handle by the bot.
This is the Holy Grail of bot programming imho. The faint of heart need not apply. Except for gold farmers, arena is why we do everything else, is it not? AFKing arena would be like missing the grand finale. Any bot movement would have to be able to be instantly overridden when there is user input so we can control most movement. Blizz must get complaints from losers all the time claiming they were beat by a bot or *****ing somehow, surely they write off most as "sour grapes." I would happily take the risk. I would also not use it very often. Regardless, I will try arena with whatever bot is available, using MrAutofight and/or Combat/Heal bot - no movement, when I get some better gear. And I'll keep watching the forum for reports from others about what's working for them.