How can you delete pics on your phone (while on computer) before syncing? Whenever I go to sync my photos to my computer I see all "pocket photos", screenshots no longer needed, and duplicate shots I'd prefer to delete.  However I can't do this from my computer where it would be sooooo much easier.  This is not just because of the UX, but also because you can see the images larger.  

I don't want to waste double the space on my phone and computer and have to do double work.  I also don't want to spend my time crouched over my phone inspecting and slowly poking with my finger when I have a full screen, keyboard and mouse interface at my disposal.

[Aside: The conspiracy theorist/negative karma in me believes apple sets this up intentionally so you run out of space faster and need to buy icloud storage or devices with larger and larger storage the next time around.]
Use Image Capture in the Applications folder. Connect your device and choose it from the sidebar, then select the photos you wish to delete and click the  icon at the bottom.

You can switch the view from list to thumbnails at the bottom too and increase the size of the thumbnails using the slider. Use ⇧-click and ⌘-click as usual to select multiple photos for batch deletion.