Alyria said:
So does that mean they are taking away that effect from divine seal then?
would be pointless for it once you get esuna.
As other people said, it will depend on what Esuna will remove. Erase doesn't remove things that can otherwise be removed with the applicable -na spell. It can remove things for which there is no -na, like Slow, Dia, Bio, and elemental Enfeebles.
It's because of exactly that fact that most WHMs get pissed off when people just yell "Erase" instead of just telling them what the affliction is and let the WHM do their job.
If Esuna just ends up being Erasega, it's still solid win, because it helps deal with nasty moves like AoE Slow and Tribulation among others.
If that's the case, you'd still also need Divine Veil for something like say AoE Stona on JoFaith.