Well, I don't know if someone has already bring this to the discution, but these are my 2 cents:
All this "we want to encourage a variety instead of duplication" thing may be true, but may be some others reasons behind.
If the goal is to end with the double stacking - wich I won't argue about it - is fine, just buff the current arcane's stats/values.
DE can tweak the arcane's rules, add cooldowns, buff and nerf those arcanes they consider unbalanced. That's not the main problem here.
The problem is the lack of honesty.
To take the arcane's rank to 5, wich all we all know means that we now need to get 21 arcanes of each type, does not benefit in any way the players. Is just more grinding/farming.
So, why DE go with this? Well, is just a monetary move.
More grinding means more players getting annoyed, willing to pay with platinum to save time.
New players will have it way more hard to maximize their arcanes, old players will have to grind more... the platinum will flow more.
Im not saying that DE will be doubling their benefits, but for companies every little penny counts.
So the thing is, please DE don't go full "this is for the players" level of bullS#&$. We got that a lot from other companies, that's why we learn to respect you in the past. Because you're different.
You want money? Is ok, I can deal with it. We all need it too.
But do not insult my intelligence with excuses.
If I am wrong, please explain me how more grinding -instead of just directly buff the stats- benefits us.
Also, pardon for my inglish, is not my main lenguage.
Edit: the fact that the next event will works as a "grab any arcane you want" does not counter all this: the event time is LIMITED. After that, good luck if you missed it.