I've used Palo Santo once in an RIS and my experience is that a little goes quite a long way. I used about 0.25 oz in 4 gal and it added a nice subtle flavor/aroma without dominating. The RIS was 13.5%ABV and I didn't actually sanitize the wood before adding, which may have been risky but it...
Just curious, but did you rehydrate the dry yeast before pitching? I've personally had much better results by doing this. But yea it would be helpful to see the recipe.