If it weren't for the unethical hackers out there, who exploit source code left exposed for ill and personal gain, the modding community, which is full of brilliant coders and loyal fans, will have to suffer. It's a damn shame.
But don't blame Blizzard. Blame the crooks and assholes who abuse open source.
The reason auto-attack is no longer visible is because Blizzard opted to remove the hot-swap from the visible UI. If I remember correctly, however, the "basic attack" icon (whether it be a fat ax, a bow, or a wand for Wizards) is red with a sword on it, and maybe something else. I'm sure left-click is still map-able to a skill.