Elemental Resistances in Dark Souls 2

The guy in the video is using the Brightbug, the effects are:

• Almost if not doubles attack and splits damage received to about half.
  
• The duration of the effect is 120 seconds, not affected by the Lingering Dragoncrest Ring.
  
• Does not stack with other self buffs.

He may also be using a Ring of Blades, the Lightning Clutch Ring, and the Old Leo Ring. I'm not familiar with the gear he's wearing but I presume there is a reason he is wearing it. Hope that helped!

EDIT:

He is using these items:

• Flower Skirt +10 (+2 VGR, +1 END)
  
• Crown of the Sunken King +5 (-1 VGR, -1 VIT, +1 STR, +1 DEX, +1 INT, +1 END, and +1 FTH)
  
• Raw Rapier +10 (highest base damage because scaling is insignificant at sl1)
  
• Ring of Blades +2 (+50 Physical Attack)
  
• Dexterity Ring (+5 Dex)
  
• Flynn's Ring (Grants the user bonus physical attack based on their maximum Equip Load stat)
• Third dragon ring (HP, Stam & Load increase)
  

From the wiki about the Raw Infusion:

Upgrades weapon physical base power, decreases stat scaling, weapon can be enchanted with temporary weapon effects. Best used on weapons that have very low scaling to begin with as weapons that rely on their scaling for damage will most likely lose damage by choosing this infusion. It can also be effective when a player knows that they won't be getting their stats high enough for the weapon's scaling to truly shine.

Most Infusions have this effect, though some not as great as the Raw infusion. Some even boost certain stat scaling, particularly Lightning, Magic and Dark, (while they might reduce base scaling, they will add FAI/INT/FAI & INT scaling respectively)

Since the Estoc has an E/E scaling in STR/DEX, using the Raw Infusion on it won't change anything. But, as an added bonus, you can still use resins on Raw/Mundane Infused weapons, which adds a base +50 elemental damage depending on the resin.