New Formulas Simplified

str 818
dex 133
atk 163

=> newMaximum == 1.49 * (4*818 + 133) * 163/100 == 8270;
(8270 - 6883)/6883 = 20% dmg increment on the higher tier.

newMinimum == newMastery * newMaximum == (20% base + 50% weapon + 10% Beholder) * 8270 == 6616;
(6616 - 3096)/3096 = 113.7% dmg increment on the lower tier. <-- Wt'f is this I don't even.

Spears/Polearms have 2 type of action ,stab and swing . So does the multiplier.
To a normal attack with spear, you will probably Stab at 60% chance, or Swing at 40% chance.
Polearm is similar, 60% Swing and 40% Stab.

But the 3rd job skill ,Crusher and Fury, will force your action to 100% Swing or 100% Stab.

At your stat, casting crusher with spear deals the base damage range 5016.8~6883.

So in fact, your min damage didn't increase a lot. (6616-5017)/5017=31.87% seems to be right.