Right now - if a tool generates an error - there is nothing productive that you can do with the error rows, these are just sent to the error log and depending on your settings the entire canvas will fail.
Could we change this in the Designer to work more like SSIS - where almost every tool has an error output, so that you can send the good rows one way, and the error rows the other way, and then continue processing? The error rows can be sent to an error table or workflow or data-quality service; and the good rows can be sent onwards. Because you have access to the error rows, you can also do run stats of "successful rows vs. unsuccessful"
This would make a big difference in the velocity of developing a canvas or prepping data.
Can take some screenshots if that helps?