I feel like my threat as paladin, trash and boss alike, is uncomfortably low.

[Reynhart]

The 1093 enmity per gcd generated by the combo has not changed since level 40 when we got Shield Oath.

Try to calculate the enmity generated by any DPS, and you'll see they're still far behind us.

Every DpS on the other hand has received various abilities that have increased their average potency per gcd

In fact, they haven't received that much more, potency wise. Full Thrust is still the highest potency for DRG, and Battle Litany don't give a constant boost.

If you see really big numbers nowadays, it's because the attack power is higher, so for the same potency, you do much more damage. Which is also true for PLD since they receive the exact same attack boost.