Atk speed modifiers stack?

I came up with some answers in search, but they were all IWAY specific or weapon specific.

Can the dervish stack atk speed increases?

It's capped at 33%.

You can't use more than 1 stance at a time, so in most cases, that's a no. If you're not limited to that, you can stack IAS skills. IWAY and Tiger's Fury are an example. TF is only 25%, so IWAY goes on top to get you to 33%. Aggresive Refrain and TF would also stack, but in most cases these kinds of skills are just waste on each other. You'd be better off with something else in that skills slot.
Like Thom said, the most you can get is 33.