Corrine viable on arena atm?

Darting Blow would work better, and Bonfire is the better special. 37 Speed +6 from DaB 3 and +5,8 or 10 based on your Phantom Speed seal is enough to basically never take a counterattack. Other than that Corrine should preform well. There are better blues (obvious we have Reinhardt in blue), but as a debuffer, almost no one else should be able to do that job as well as she can.

I use her with swordbreaker and panic ploy (she is +HP with HP seal) and she does just fine.

Edit: She is also an amazing answer to Sigurd.

F!Corrin is viable indeed but not with that build of yours.
Her key stats are Spd and Def, so she can indeed make use of Windsweep but if you choose to do so, then don't give her Armored Blow...?
You're supposed to sweep then there is point in having more Def if they don't counter-attack. You can give her a cheap Darting Blow 3 instead (Florina 4*)

All in all, she is an inferior version of Nowi but much more common so you can heavily merge her in order to make her more effective as a unit.

Everything depends on the way you want to build her. I use mine as a physical tank (screenshot below, in french sorry >w<), but a Spd boon should help her work as a tanky attacker. Don't expect her to obliterate everything, that's not her role, but she can easily bait a physical attacker and use her debuffs when you need it. You definetly can make her work if you relly want to use her instead of the top blue threats in the arena. Here are my recommandations :
Weapon: Dark Breath (Lightning Breath isn't good on her)
Command: Swap (to let her take the hit and potentially save one of your heroes) / Reposition (always a safe choice)
Special: Bonfire, and only Bonfire (sometimes it's her only way to deal damage, you can even kill B!Ike and Hector sometimes)
A = Depends on her role - Armored Blow (player phase debuffer) / Steady Breath (bait and punish) / Darting Blow (double people for Bonfire) / Triadept (if you hate Falchion so much) / Fortress Def (for that mean defense)
B = Quick Riposte (bait and punish, will secure a kill on a red physical unit) / Drag Back (very useful, especially in a tanky debuffer role) / Lancebreaker (depending on your team) / Windsweep can be nice, try with DartBlow but remember that you will not kill every unit in one round
C = Really up to you, but here are some of the best choices - Threaten Spd (double attack to Bonfire is a nice combo) / Thr Res can be useful too / Hone -anything you need- (Hone skills are often a good choice since you want to stay close to your other heroes) / Savage Blow (to add some "debuffs" if you want too use Fortress Def)
Seal : Phantom Speed is a good choice, you could also consider trying Distant Def (or maybe Panic Ploy)
Anyways, you can take what suits more for your team or just what you'd like to play. Corrine is a really fun unit to use (you'll see a lot of 0x2 with all these new recent heroes) !
(My Corrine's skills = DBreath, Swap, Bonfire, ArmBlow, Drag Back, Savage Blow, Distant Def; with Summoner Support and S Support with Iñigo)

She is a very good counter to Brave Lyn if built correctly. She is very expensive to build but very worth while. You have to build her as a full physical tank but she will serve you well. Just be sure to have someone who can cover her against mages and specifically Julia and Deirdre. This is the build I use for reference.

Lightning Breath+
Swap
Ignis
Steady Breath
Quick Riposte 3
Threaten Res 3
Speed +3

Optimal IVs +Spd- Res or +Atk-Res

I want to add, don't forget Dark Breath+ upgrade! If the Feh Channel buffs are the same for every weapon, you can use a +4 Def upgrade to make her pretty tanky and increase Bonfire damage output (with a Fortify Dragons buff she's a beast). Also you can use the +3 Spd upgrade to make her quite fast and avoid a lot of doubles. The update will be released next week so you have plenty of time to think about that.