From what I've read of the class on www.finalfantasyxiv.com, I'm leaning to believe that they might be a dex based damage dealer. If that's not the case then we might have to redistribute our stat points if we're tanking or substituting tank.
The abilities for tanking with Pug are definitely based on evasion. I'm sure you can use some abilities from other classes to make it more defense or HP based, but the tank abilities native to Pug, that we know of at this point, are evasion based.
If evasion is going to come from dex again(I don't see why it wouldn't)and Pug damage is str based, we won't be able to go from DD to tank on the fly. Of course we could also build a hybrid DD tank type. We could do both but perhaps not be as effective at either.
I'm curious to see what other people think here. Any thoughts?