Both seem to be wrong. Here's the Taunt from Prelude.pkg (first line is from lvl1 and second from lvl12):
<level duration="1.8" percentMovementSpeedBonus="0.5" shieldBlockChanceBonus="0.50" shieldDamageAbsorbBonus="20" percentMovementSpeedPenalty="0.70" range="4"/>
<level duration="4.0" percentMovementSpeedBonus="0.5" shieldBlockChanceBonus="0.50" shieldDamageAbsorbBonus="20" percentMovementSpeedPenalty="0.70" range="10"/>
You'll notice that only the duration and range change, the shield block stays the same.
Also I think Seeker does have a chance of blocking even without Taunt, but couldn't find any data to prove that now.