Yea, this has been the case since I've started playing ARC a couple months after release. And I can understand why, since the two together offer a very OP situation (specifically when combined with Trifurcate/Multishot).
Though I haven't tested post-1.18, Ferocity and Raging Strike always did very, very similar damage boosts. This of course could be completely different now and I suspect it is.
As far as the over-writing, it depends on which you pop first, whatever you use last will be the bonus you get, so I've found that I like using:
2x Multishot post-fight/1x Multishot mid-fight, Ferocity II + Quelling Strike II, loose arrows.
Trifurcate + Raging Strike II + Hawk's Eye, loose arrows.
At that point, since Ferocity's CD timer is a bit lengthier, I usually use Quelling Strike with a weaponskill and usually the timers will sync pretty closely then.
Of course it's all situational. This is just a "copy+paste" kinda rotation. Likely not the best, but good damage output at an even pace.
