Please Note the Little Bar "Attack Indicator".
Try to time Attacks with a full or not visible Attack Indicator.
The Attack Indicator, Since MC 1.9
Was In Place to allow for "Critical" hits (Maximum Damage).
As in the Picture Below,
Time Attacks with the Attack Indicator with the full bar and a Plus sign ( + )
Learn from Experience of Playing MC your Foes. (Works For Monsters or NPCs only.)
Jump Up then before you land Attack with Full Power for additional Damage. (Works For All Monsters and Players.)