Fall damage into one high water seems to still have issues in 1.4.4. So far I've only been able to test the problem with witches but it may apply to other mobs too.
Witches falling from Y 63 to a solid surface at Y 14 covered by a one high block of flowing water survive. As I understand it fall damage is equal to the height fallen -3.
This gives us 63-15-3 = 45 So fall damage onto a solid surface at Y 15 would be 45
One high water should protect the mob from from 16 of the fall damage giving 45 - 16 = 29
A witch falling this height should take 29 fall damage which since witches have 26 health should kill them. All witches are surviving in this instance.
Sorry if I've put in an unnecessary report due to faulty math or flawed understanding of how water is intended to work. Thanks for the time taken to look into the issue.