But the dollar is 50% USD vs. 50% "basket." Whereas USD/JPY is 50% of each. It's just as much moved by the other random currency I chose.
I don't think you understand the problem. If a currency moves, it could either be the base currency or the quote currency. If you trade against a basket one random currency in that basket could move and completly negate your dollar move. Why wouldn't you just do your homework, dig a little deeper and find an edge?
I understand that could happen. But it's a lot less likely than trading directly against 1 other currency. As far as I'm presently aware, there is no better way to track 1 currency than against a basket.
There's simple TA and than there's advance TA. Both can be effective, although for most people generally speaking I'd say simple TA is their best shot at a trading career or producing any type of consistent money. There's nothing arbitrary about it, you can literally pull up a blank chart and see that TA works. The only question is how bad do you want to make money (how much money does it take to make it worth your time), are you patient enough not to take bad trades and do you have the mental fortitude to execute your plan on a consistent basis.