I know nobody likes the idea of going back to having a tank... But, yah, the game was designed with a tank in mind... from like, square one, you all knew what you were getting into >:I. Still, You have 2 choices when it comes to DEF down.

Unsuck your lazy ass mages and teach them the power of Erase.

or use an actual tank and follow Okipuit's Advice.

You dont need a PLD, a WAR Tank can tank just as well, Focus Erase on the main tank, rather it be WAR, MNK, or DRK... then the lesser DD can pull back until its removed. "ZERGRUSH" was a strategy we adapted as a community, and the reason is because its pretty fool-proof and requires the least amount of brainwork from anyone involved... long story short, its a strategy for idiots that happens to be the quickest route when the group is good.

So, this is not to say everyone uses ZERG is dumb, But its a strategy intentionally designed to "Kill it before anyone needs to use their brain" (I.E Cures/Erase/etc)... which is also why Perfect Defense plays a part... even less brain power involved. So, now, We may have to actually begin to readapt the strategies they intended us to use, or at the very least, (POINT ONE) - UnSuck our terrible mages who have grown dumb over the years due to dulled strategies.

If our mages can learn their jobs again, this whole update is a none-issue. Assign a "Main" Tank to be kept alive, PLD, WAR, etc... then teach the mages to focus on certain debuffs. Might actually have to rework party structures a bit, RDM might be thrown back in for assisting in -Na/Haste/Refresh Cycles so the WHM/SCHs can focus on Healing/-Na spells.... instead of one inept WHM trying to do it all and "WIPE AND TRY AGAIN" when Perfect Defense wears off.

Okay, If i sound a little jaded, i might be... Basically, I don't see this update changing anything for good parties, good teams, and smart people... We'll adapt, make a better strategy, and maybe become a little less Zombie-mode. Sure, it won't completely remedy Zerging, but at least it'll make some people rethink the best party set ups for mobs to include contingencies like needing Erase, a designated "oh sh*t" tank, so on, so forth.

Its not the end of the world. We will adapt, and I think it'll serve to make, at the very least, Mage jobs far less mind numbing and involved.