Thanks for the detailed feedback and scanned image, very helpful!
Did this issue exist before the drum was changed?
This looks very like there is a problem with the transfer roller as very little toner is getting deposited.
The transfer roller uses an electrical charge to get the toner from the cartridge’s drum unit onto the page.
Sometimes, it may be incorrectly positioned in your printer, causing very faint prints.
Try to remove it and insert it firmly again. When properly inserted, it should be nice and flat.
(If you’re having trouble removing it, be sure not to break or rip it out!)
Do not touch the surface of the transfer roller with your hands as this will make the problem even worse.
You can try wiping the surface with a dry cloth or use a can of compressed air to blow it clean.
Let me know if there is any improvement when you do that?