I also have almost the same problem with my Canon printer. It prints perfectly (somewhat high quality) from web page including the black text. The print quality especially the black prints getting worse when I print documents from M. Office. And even worse when I print documents from M. Work.

That's why I plan to buy a new printer since the above scenario doesn't make any sense to me. I tried to adjust the print quality from the menu and it still does the same thing.