[apocalypse80]

I've tried at 2000 and I got a char that really was impossible to hit , even for toxeus.
Of course his spells still hit.

My guess is that a DA a bit over 2k should be plenty.

For reference , VERY few things have over 1k OA or DA in legendary.
And most of them are heroes.
Of course monsters with specific skills (like battle rage) can get much higher.

Which pretty much makes 1k in OA and DA recommended values if you don't want to suffer offensively or defensively.