For me, the entire purpose of a keyboard shortcut is efficiency. It's meant to be faster.
Why is 'assign task to me'
(Left) Alt + Shift + .
That's 3 buttons, and to make it worse, requires both hands!
Maybe take a look at other software and web apps such as Gmail and how they have one button (eg. p/n for previous/next message in an email thread) or occasionally 2 keys together, but always doable with one hand, otherwise I have to take my hand off the mouse and it's no longer any faster than just doing long, slow multiples clicks with a mouse.
If you're worried about people accidentally hitting shortcuts, allow us to turn them off. Or customise them. Just please, don't force them to be really silly, complex 3-button shapes that are really intuitive and spread across the whole keyboard!