I think the new system is more for game pad users who don't have the want to take their hand off the controller to use the mouse for a quick target selection.

The status bar vanishing is a feature that popped up after the march update I think they are working on it.

You can turn off the auto target lock of things like spirit dart in the configuration menu. Spells don't lock you because it would suck to be locked on a player after casting cure.

I'm aware you can't select dead players and I think you should be allowed to target them normally whenever too. Maybe you should make it a suggestion, I'm not too sure if its a bug since its like that for everyone.