Rdm in 5.0?

[Archwizard]

Corps-a-corps and Displacement are the core of Red Mage?

Believe it or not, the driving force behind most design intent is archetypal aesthetics. You can apply that to most jobs: from classic war wizard aesthetic for the Black Mage to the Naruto mudra shuffling of Ninjas to the rhythm gameplay of Dancers. In our case, the aesthetic of balancing white and black magic, of weaving magic with fencing, of agilely flipping in and out of action -- trying to fit the "jack of all trades" imagery into a pure DPS with supportive utility.
Taking the visual image of "I'd like to see this" gives the devs a kernel to build around, and defines or influences what a job should and shouldn't receive in the future.

I'm not saying you're wrong that having our flips influence our damage output is a bad idea -- it's one I wholeheartedly agree with, and believe that our mobility tools should be conserved for said mobility -- but in seeking to fulfill the aesthetic, the devs wanted to create an incentive for us to use the flips regularly (as opposed to just sitting in melee, auto-attacking between casts for bonus DPS, never touching Displacement). We can agree that they chose a poor incentive and discuss better ones instead, but simply saying "that's dumb, remove it" is a slap in the face to the design intent.

What you spam is Fire II (or at least it was, I've not checked in with Black Mage in a long time).

Hasn't been Fire 2 for a long time; nobody really uses the "II" spells as BLM anymore.
For SB it's been more a weave of Bliz3, Bliz4, Fire3, Flare x2, Transpose, repeat until Foul and sprinkling Thunder 4 as Thundercloud procs pop or the DoT falls off. The changes in ShB will hopefully replace the Bliz spells with Freeze, asserting more area damage into the AoE rotation. Big reason we're not including oGCDs here is 'cuz its cast times are longer than its GCD, unlike SMN and RDM, and their CDs are longer than most trash pulls.
Point being, much like SMN, way more active than "spam Scatter till it dies".

Now that I think about it, actually... It's a shame Acceleration still has no place in the AoE rotation... I always wished it would get adjusted to force a Scatter proc, since that would give you one more thing to remember during AoE rotations, but with Scatter gone that's no longer a possibility...

I can understand why they didn't, though. Scatter procs gave 20 Mana, second in gains only to our Verfinishers, while the other options we could produce only gave 9 Mana apiece -- and the act of using the proc in itself gave a chance to proc another.
I know I for one have popped an Enhanced Scatter in single-target just for the speed. Sure it was a direct damage loss, but dropping a Jolt for it also saved multiple GCDs on the way to our melee combo.
Trying to rebalance this (or at least iron out the unintended niche) may very well have influenced the decision to remove Scatter.

I'm also honestly not seeing how the new rotation is a faster buildup actually...

In fairness to this point, the rotation does slow down slightly once you pick up Impact (as each of the quickcasts produce 7 Mana of their respective types while Impact produces only 6 total), which is a point I hope they will change.
Even at Impact 4/4, you'd be 41-34 which while below 10 Scatters with 2 or more procs, would be stronger than one proc and still be more reliable, not to mention generally less mindless.
Personally I hope they go the full 9 yards and tweak it to give more Mana based on the number of targets hit.