Diablo 1 HD Hellfire Mod | Awake

I've a Bow of the dead but my dps at lvl 21 is 294,23. With a normal yellow bow my dps is 344.36 but the yellow bow doesn't have Ignore target defense stat.

Is it worth changing or is the stat better?

The ITD (Ignore Target Defense) helps with 2 things:
1-Increases the chance to hit the monster;
2-Increases the physical damage dealt;

For more detailed information: http://awake.diablo1.eu.org/ignore-targ ... %20defence

In the late game (Torment difficulty) ITD is NECESSARY for Rogue (there are 2 unique bows that have ITD, the best one is HeartSeeker).

For your current situation, I personaly believe that the bow with ITD is better, but it should not be a big difference at all.
You can also just test it. Have one bow in each hand. Kill a monster with the first one, and look at the damage dealt. Then switch, and kill a monster of the same type, and check which one showed more damaged dealt.

Theoretical question.

At what total +% To Hit does any weapon approach ITD levels?

As in, with all gear that increases % To Hit, what cumulative bonus is roughly equal to ITD?