Another thing to consider is that you may get more damage out of adding STR or DEX than accuracy. It's hard to point out the specifics (since it depends on a lot of things), but Accuracy is not the king for multi-hit WS's.
Acc is the king for multi-hit WSes. Until you hit 95% hit rate it is point by point the best return you can get.
It is possible for pure STR or pure DEX to beat acc in terms of return. But that means that either your fSTR is very negative, or that you have 50 dex. The first thing is possible to happen, but unlikely. The second isnt even possible.
In short: The only way for pure STR or pure DEX to beat acc is when your base damage is already very low, or when your acc is capped.
More important than STR or DEX though is atk. Especially for jobs that have lowish base attack ( THF and DNC ), atk usually gives better return on multi-hit WSes than secondary mods.
Thats why people say that for multi hit WSes, ACC>ATK>Secondaries
There are exceptions, of course, because after all this is Final Fantasy, not WoW. But that is a pretty good guideline to follow.