Dear DPS.

[kasuke06]

tanks have significantly higher potency. I was stating as though both start at 100. therefore their potency is their damage.

Stances(shield oath and defiance) generate no threat on their own, they double the current multiplier of the attack.

I'll be a little more realistic this time and include the damage reduction from stances.
112.5(heavy swing no multiplier)
187.5(skull sunder x2 standard)
225(butcher's block x5 standard)
leading to 3112.5 threat generated(112.5 + 187.5x4 225x10)
the last combo I linked(this without the stances weakening effect and multipliers from stances) would come out to 2150 without stances, or buffs.

tanks have extremely high potency attacks, but few if any ways to employ them quickly like DPS(BRD can use off gcd attacks to fill black spots where a tank has to wait for a gcd to go through, before using anything other than a buff. MNK get a speed bonus from GL stacks, dragoons... they kind of play like tanks without the enmity bonuses.)

EDIT: Derped on the combo from the first example bit.