For Defensive concerns the rules for concealment are very clear...miss chance and with total conceament, you can't be targeted visually.
Is there any effect on an attack for a creater attacking WITH concealment less than total concealment.
For this scenario, lets assume the target has no concealment or means of bypassing the attackers advantage.
my understanding is that concealment miss chance only applies to a defender. An attacker with concealment can reach around or otherwise bypass it as (s)he sees fit. ie-the spell blur grants the target 20% concealment, but does not state anything about it affecting their ability to target others, and can thus attack as normal.
