Silveras said what I was about to say. Just look at the monsters and you'll see it clear as day. Bonuses from synergy stack. They even stacked back in 3.0 regardless of it being a "named" bonus (in fact I'm certain there was a direct statement of that being one of the "exceptions" back then anyway) as can be seen by the stats of the iconics and the wording of the books. At any rate, they stacked then and they still stack now.
Besides, it makes sense. If you have two skills that help a single skill, why would one suddenly not help that skill just because you have another that does?
Um, anyway, that's all I have to say.