I understand your concern, but try to organize it like this:
Choose C and D as volume backups, and E as file level ("hybrid solution"). Then schedule it on a 2 hours backup or however you want it. Because we are incremental forever, you only protect the block-level changes, and this will be 95% your digital image files (I know this one very well
). The little overhead of having the two other volumes also every 2 hours is extremely low, and since we use a method to keep the backup in background mode, you won't even notice the backup even if you are doing some heavy-lifting editing and rendering that takes all of your resources.
Now of course... Don't believe me on my word
, try it out and you will see