The Chosen Ones

I suggest u boost your hp as high as possible.
In chapter 1, black merchant sell spell book Divine Seal that make u immune to magic in 5 seconds. Cast Divine Seal on Fradz and Phodom healing himself while still running ofc.
An other point is movement speed, if u hav Aerial Shoes, put in in your box and move box to the middle of the circle( where u fighting him), your party should be still on Aerial shoes's effect cuz its an aura
If u still find it's hard, my last advice is F10-> Gameplay then change game speed to slow, this will help a lots
I notice that even his spell is so powerful but he is fragile, so while he is vulnerable to attack, throw as many spells in him as u can
I defeated him on extreme and hard so keep trying, u can make it 

yes the wind boss is hard, in my opinion even harder then john.

my tactics ( u could loose 0-3 life cause of fradz low hp and unlucky spawning hurricanes, after 3 restarts i managed it 2 survive with 0 deaths)
- u need movement (arial shoes on phodom, he shouldnt die cause he is the healer and tank)
- u need **** dps on fradz and lvl 10 lifesteal king (siphon life) and lvl10 force blow
- on phodom lvl 10 natures armor
- give the power hammer 2 fradz 4 more dps
- phodom should wear only life boosting or heal items, best are holy seal, trinket of righterousness, ancient leaf, legendary murloc head
- u can steal staff of tranquility from the boss so let fradz wear thief set at beggining (change it with a better dps item later)
- when the boss casts... RUN AWAY
- when he stops auto attack, RUN AWAY
- all other time nuke him with your ultimates
- especially fradz with sword dance and then teleport srike, u can also go invisible with fradz and so easy ascape the hurricanes
- but dont let phodom die u can heal him almost instantly when u have shield of fire maxed every 10secs.
- if he spawns trees (near the end) aoe stun and kill fast

its kind of special, because not everybody have the same build, but the main things are similar
have fun

Woow, I did not have those nice equipments in my first play through, so I decided to give up.  I just couldn?t beat this guy.  Will take my revenge on this second play through.