One thing the article doesn't mention but the paper goes into is the syllabic complexity. Vietnamese and Chinese both have a ridiculous amount of tones (from a Western perspective). From the paper:
Language Syllable Set Weighted Syllabic Complexity
English 7,931 2.48
French 5,646 2.21
German 4,207 2.68
Italian 2,719 2.30
Japanese 416 1.93
Mandarin 1,191 3.58
Spanish 1,593 2.4
English gets the density from a huge syllable set and an average syllabic complexity. Mandarin has a fairly small set but high complexity.From my experience with Japanese, it seems like it has evolved to compensate for the low density:
A lot of the pronouns (I/he/she) tend to be dropped and assumed from context
Some verb forms take the place of longer phrases: taberu koto ga dekimasu->taberaremasu
In spoken/casual usage, many phrases are shortened: oiteoite -> oitoite, my personal favorites are the arigato gozaimasu-> mumble-zaimasu or the irrashaimase->mumble-mase