What they mean by "change the damage calculations of tanks"?

[Ultimatecalibur]

Now that I think of it, didn't they say they had lower level accessories than dungeon gear because they didn't want crafted accessories breaking progression like in Coil?

Pretty much. The whole reason for the 3.2 changes to Materia melding and tank damage calculation is because as they stand now pentamelded i150 crafted accessories give a benefit comparable to i260 accessories.

3.2 is likely to be the first patch since 2.0 that has accessories with ilevels comparable to the best crafted gear on release.

Then don't start by going backwards and making all jobs basic. Start by supporting the tank accessories remaining as they are and the other jobs getting additional options too.

They needed to. Pentamelded Str/Vit accessories are scaling to well for tanks. A 10 ilevel increase on level 60 gear raises a non-crafted accessory's primary stat by about +2.5 but currently increases a pentamelded accessory's primary stat bonuses by twice that.