Click is still in the game and works fine. However, only the first click seems to function. So if you have a vehicle macro, to click buttons 1, 2, 3, and 4, and normally spam the macro, after the patch only the first /Click command will execute.

Or if you have a Click Castsequence, with a spam macro which clicks several other macros, only the first Click command will be recognized. This means, the other macros/sequences will never execute, by spamming the master macro which you current spam.

Given that, macros will still likely execute top-down. So you might be able to do:
/Castsequence Spell 1, Spell 2, Spell 3, Spell 1, Spell 4, Spell 1, Spell 3, Null
/Click MultiBarRightButton12

And have on that button:
/Castsequence Spell 1, Spell 2, Spell 3.... etc

Which gets us a double length macro, by utilizing /Click. But does not let us utilize /Click for perfectly timed (assuming consistent spam speed and tweaked castsequences) DPS of multiple abilities in a priority sequence.

Commas are also removed from castsequences, so we cannot use them as a timer mechanism.