I don't think so. My work is mainly Office-based too. I stare at text all day. My 27" 5K monitor gives me 2560×1440 real estate (which I consider necessary to have at least two windows side-by-side) and pin-sharp text, which is just perfect for my needs. A "4K" monitor only gives me pin-sharp 1920×1080 real estate; that's not enough for me (yes, I tried).
So, the Studio Display's price aside, a 27" 5K monitor is definitely not overkill for that kind of work IMO.
A "1080p" monitor doesn't provide pin-sharp text on macOS BTW.