Hi I have moved from Photoshop to Krita for around 2 months now.
So far it's okay to support basic drawing process, but not for photo retouching or effects and such.

Below are some tools/functions that would really make things more efficient:

1. Allow importing only images from PDF

Instead of importing the whole page, add another function that only imports the images in the document will be really handy.
Most of the time I only what to abduct the images as a whole from the PDF without using screencap in my computer.

2. Allow previewing pages before importing the PDF

As I can save time from opening the PDF separately outside of Krita to check which pages should be imported.

3. Separate pen and eraser tool

It's been annoying that whenever I want to erase something, I have to press one more button (B) before pressing E.
Also it's very inconvenient that changing the opacity of the pen/eraser will simultaneously change the opacity of the other tool.
Most of the time I just want to draw with a translucent brush but erase it completely if I made a mistake, but to do so I'll have to change the opacity each time I switch between these two tools.
Separating them as well as their settings will make the whole process faster.

4. Allow layer/group effect

It will be super handy to be able to add a removable stroke/shadow/gradient overlay effect to layers and groups so there is no need to duplicate back up layers in case I changed my mind later.

5. Edit text on canvas without having to click the apply button every time changes are made

Also allowing the changes made to the text (eg. font, colour, size) to appear on the canvas immediately will allow us to check if it fits its surroundings quicker.

6. Allow split screens

Whenever I want to pick colours from another image, I have to click between two tabs as one tab occupies the whole screen.
Having two or more files to be laid out side by side will be really convenient when I need to pick colours / drawing according to reference.

7. Add timeline to make videos and GIFs

A 2D animation function that allows tweening of keyframes and exporting of GIFs will be really convenient, saving time from exporting images to another software.

8. Add stamp tool

When some pattern/texture needs to have their holes filled, a stamp tool will really be helpful.
Now it can only be done by selecting a nearby area using the selection tool > pasting on the hole which is not efficient