Damage shield appears to be 86 HPs on level 85. My druid was doing 214 damage per mob hit and that's with this pot stacked with 2 druid DS buffs worth 95 and 33 HPs. 95 + 33 + 86 = 214. :)
Paid 750pp for this pot while level 13 seems to sell for about 250pp. The XIII pot does 75 damage per hit, 11 HPs less. Don't think 11 HPs extra damage is worth 500pp so prolly sticking to XIII unless I find XIV for a lot less.