Linguistics just doesn’t deal with definitions like that. It does mean that, and certainly even connotatively historically. Today, in modern parlance, it definitely means “to kill a large portion of” something, and is almost never used as a 10% reference. So your team could be correctly described as “decimated” in both scenarios.
Decimation means “lose 10%”, not “lose all BUT 10℅”
If two people suddenly quit your twenty-man team you’ve been decimated. If eight or eighteen people quit you’ve been devastated.
(Plus a bunch of “politics” and civil rights things.)
Linguistics just doesn’t deal with definitions like that. It does mean that, and certainly even connotatively historically. Today, in modern parlance, it definitely means “to kill a large portion of” something, and is almost never used as a 10% reference. So your team could be correctly described as “decimated” in both scenarios.
Dictionaries are free to note whatever definition they want, but so is everyone else
Great answer
Worked in a company that decimated their workforce with redundancies. I word it correctly and other people wrongly assume it means something else.