The answer is there, although it not be plain as day, I'm sure you can come to a reason...
Hint, it lasted too long, and was being spammed...
your not stupid, so let me explain this to you ;
If firewall is now lasting less time when casting multple firewalls, our DPS has and will take a hit, someone mentioned that because we are having to refresh firewalls we are spending less time casting our offensive spells (IceStorm / FF / Firebang / Lightning), thus losing dps.
So yes, the actual 'damage' of firewall is indeed the same, but our OVERALL dps, is significantly lower, couple this with the idiot flinch changes that were made last week, add into the mix that sins have no cooldown on swiftfeet, add again the fact sins gain all their natural stats from helmet/armor/weapons (ACC/AGIL), oh and that stick the ever so small but very noticeable FF delay (Yes i know its shorter than euro, but its still significantly more than other servers over the past X years) and what you have is a wiz class who feels **** (Some people will disagree)