How good is refined jaffar

Ye like other people have stated: hell be super good for story and ghb and such but not as much for arena...unless healers start becoming more common

Give him Windsweep. He can then safely attack anything besides dragons to trigger the damage and stat debuff of his dagger to anything else in the game.

I've been using him in Arena for the past few days...
He's pretty good I'd say.

atm I have him set up to do as much effect damage as I can manage:
B: Poison Strike 2
C: Savage Blow 3
S: Savage Blow 2

I find him to be super strong against specifically Armor Emblem and Infantry teams.
Against Flier Emblem he's meh; and against Horsie Emblem he's pretty poor. Mixed teams he's also pretty meh against.
He also has some troubles with map layouts that make both sides have to split up their teams.

Jaffar is pretty easy to use effectively as long as you have a multi-threat wall to hide him behind after he makes his first attack - A dancer helps a lot too.

What I like the most about his game is if he attacks once, you pretty much win that game outright. The ability to knock all your opponents units down to half health without procing any specials is straight up overdosed.
Its honestly the coolest.

I feel like if you're not using him for Arena Defense there are some interesting opportunities you can use in his skill set.

In an Infantry Pulse team, I think he might be the most ideal user of Growing Wind because its eff covers the same field of damage as Savage Blow so you'll be able to get some interesting plays off where you knock a whole team down too 1 hp all at once.

After using him... His B slot offers the most opportunity to be creative.
Windsweep is okay, but I probably won't be running it. His weapons signature effect is enough for Offensive Arena + running Cancel Affinity or a Breaker skill seems like a better fit for me because I'd want him to cripple teams while also securing a kill by himself.

I think what he does best is he fills a niche in teams that specialize in enemy phase units.
You can't do much approaching except baiting, so having a unit that can bruise whole teams and then get bounced out of danger is extremely useful.