With the patch update on 19th February to Version 1.8.3. there came weird changes in the mechanism how mobs function. Suddenly every mob I encountered so far moved and/or attacked multiple times faster than normal. Meaning that they walk or run much faster, attack faster and in between attacks there is less time untill they attack again. I recognised that when I hit a mob it drops fast to the ground than normal. Everything depending mobs (not just hostile mobes) seems to be sped up. The rest of the game is running regularly. So the day-night cycle is normal, breaking is at normal speed.
You can also see some examples in the attachment. I don't have or had any mod installed. The yellow circle in the middle of the screen in the "examples"-video comes from the recording tool.

I already tried to fix the problem by re-installing Minecraft and Java several times. Also I synchronised my systems cock with the internet time and tried to change the affinity of javaw.exe, since both may effect the game. But nothing helped.
In addition I checked if older versions were impacted by the issue and therefore tried 1.8.2. in which the same problems appear since 19th February.