i'd never sacrifice main stat for def at 1:1 ratio lol, but maybe that's cuz i'm evie and i dont care about def that much.
The problem here is that Attack will eventually cap out, and the returns diminish as you approach that 10k cap. It gets to the point where that, if you have 14k attack (easy enough if you have a +12-13), it's more beneficial to invest in defense then attack as even if you stack attack to 15k, you won't do that much more damage for each hit. Meanwhile, a thousand or so defense will easily half the damage taken by some raids if you're still in the lower (see 6k-7k) region of defense.
Of course, this doesn't apply much for Evies as they have to sacrifice too much in order to stack Defense. However, for Lann, Karok, and Fiona, this is a completely valid tradeoff.