The only problem I see with your logic is that Temp. Axe will remain a viable mainhand weapon, which unless it gets introduced into the Magian Trials to increase its damage rating, will begin to fall short compared to other weapons.
There's already the OAT axe in play (Punisher DMG:46) which will only become better as more trials are introduced... so while yes, I love Primal Rend, it will become a nice little weaponskill for rather specific situations.
Rampage as far as we know right now will probably go back to being our top ws, unless the new one(s) being released perform better (though I doubt that from what we saw in that ws demo trailer).