Make player vs. player battles possible

Background
In Poland we have huge PVP servers divided to "sectors" that can host 2000-3000 players. MMO Hardcore survival is like culture here but few months ago it froze even more - on version 1.7.10 or 1.8.

What's the problem?
Protection 4 is the strongest enchantment for armor.
Sharpness 5 is the best enchantment for sword.
Strength 2 is the best thing you can take to increase damage.
Now, if you combine these things together - even with strength 2 you'll get a fight like in minecraft classic - no fight - both players are invincible.
First option: click at other player in best rhythm you can. You'll eat sometimes, he will, no one will get killed (yes, we know about durability - let's wait 5 minutes until someone's armor break)
Second option: run from the person? of course, you can - your health bar regenerates fully just after few blocks away from the enemy.

String[] arguments:

• "On our teamspeak servers more and more people ask us not to change version"

• "Tests on 1.9.4 gone bad: you can't kill person with naturalRegeneration, but without - you can't heal"

Why it's so important?

• 90% of reasons why our players are players is direct PVP (just hitting each other).

• Creating tnt traps, killing with potions, even every other method is not satisfactory.

What we want?
A vanilla-implemented system of working PVP.
My sugestion: regenerate health from saturation effect 4 times slower.

To game devs: what was the point?
What was the point to make best items too overpowered?
To have move creative players and kick PVP kids from the game?
If the above reason is incorrect, now the whole problem is just a bug.