In Expert worlds defense is calculated different way than in regular world. Instead of: defense value / 2 = flat damage reduction (for example: 100 / 2 = 50 flat damage reduction), it’s: defense value * 0.75 = flat damage reduction (for example: 100 * 0.75 = 75 flat damage reduction).
This means defense is much more effective and important in Expert mode. Of course even with maximum defense (about 150, 113 flat damage reduction) it protects you against weapons like Meowmere only slightly better.
However, 1.3 (earlier versions partially too) gave us few changes/additions to the game which helps more - percentage damage reduction. 15%/30%/45% is granted by Bettle Shell armour set buff. 30% is granted by Solar Flare armour set buff. Worm Scarf gives 17%, Frozen Turtle Shell gives 25% when below 50% HP and finally Endurance potion 10%.
If my calculations are correct, maximum damage reduction is: 45% + 17% (or +10% - unfortunately Worm Scarf doesn’t stack with Endurance Potion) + 25% = 87%. That’s a lot! It makes a huge difference.
Yesterday I was fighting with a Meowmere spammer. Full DPS loadout - Avenger Emblem, Warrior Emblem, Mechanical Glove, Fire Gauntlet and some other two damage accessories (he had UFO instead of wings). I’ve been able to survive few hits and kill him easily, with remaining HP at about 200 - 300. Before he returned I’ve managed to heal almost completely with the Shiny Stone accessory. This repeated many times. The only unfair advantage he had was extreme lags - he could appear on my screen out of nowhere and deal serious damage before I could counter attack.
My personal loadout is High DPS Tank - 94 defense, 47% damage reduction (72% when below 50% HP), Meowmere at about 460 damage and Terrarian at 420 damage. With this setup 600 damage Sniper Rifle will deal: ( 600 (weapon damage) - ( 94 (defense) * 0.75 ) ) * 0.47 (damage reduction) = only 249 flat damage! This allows me to survive two 600 damage hits (even three if I heal with Super Healing Potion), and gives me enough time to kill the enemy or retreat to a safer spot. Same thing with Meowmere, Terrarian, or other highest damage weapons. Damage reduction makes a real difference.
Of course, this only regards when fighting against single target or few targets, as being surrounded with Meowmere spammers will definitely end with your death (if you don’t RoD away).
I do no excuse weapons mentioned before, nor I think there should be no restrictions regarding their usage. There has to be a way to balance PvP without the need to ban most new, highest tier weapons.
ps. if something is unclear, tell me, my english is not good enough.
UPDATE
Today I’ve been fighting with novices. One was mostly spamming Meowmere, others were using some other ranged or magic weapons. Reached +25 ks until server crashed.
I find Terrarian a good counter to Meowmere on the right spawn arena. If an enemy was using Lunar Flare against me, I got below him and used my Star Fury, with good aiming and damage reduction I killed him much faster, than he could