Rifts have an increased droprate compared to anything outside rifts.
No point discussing while we can't see your item stats.
For one, you're not using F+R but only one of them (if that is even Focus/Restraint). The other is that you have different bracers.
I really don't understand what you want, both bows area already rerolled so there's nothing you can do.. 1% ias isn't going to make the difference, but the RCR is. I'd go for the one on the right.
1. You can reroll Nat's legs to Nat's slayer. (but it will NEVER be ancient with the set exchange recipe)
2. You can reforge your Nat's slayer to try and get it ancient.
Or upgrade some rare wands until you get a new WoH. Shouldn't be too hard.