I'll pre-face my comment with the fact that I'm not a high level RDM here on Nasomi yet...

But wouldn't Evasion on RDM suck no matter what on anything of significant level? Wouldn't it be more worthwhile to deck out in -DT gear instead where possible?

That's what I was thinking. Anything you fight that requires some effort will just have huge acc due to rdm's shitty evasion rating + level difference no? Things seem to fall into one of two categories here. Easy as heck to kill to the point where evasion is meaningless, or hits like a truck and you gotta blink tank + kite it; an unfortunate consequence of level difference penalties.

I suppose if you're fighting something around lvl75 you could get good evasion with blind2 + evasion gear, but then you can just sleep->nuke anything anyway?

I just think it'd be wasted inventory. Decked out Evasion sets work out much better on NIN and THF due to their already high natural skill caps. The gear just pushes it that much higher.

If you work on some solid DT sets, and stack available defensive buffs, it'll probably be more beneficial in the long run. Also, in a situation where you might get wrecked, try casting Sleeps (and other defensive spells like Bind, Gravity, etc.) in partial DT along with self-buffs to help reduce your chances of being interrupted. On retail, using sets like this allowed me to have a lot of fun on BLM that otherwise would've been pretty deadly.

Again, I'm fairly new here and YMMV here on Nasomi.