The secret to defeating Frostbranch is hitting him frequently with mid-level spells. Train Sun school enchants to increase your accuracy and pierce, that way his Smokescreens and Tower shields won't bother you so much. Use mostly traps instead of blades, since he loves using Earthquake against you.
As soon as he puts a Smokescreen on you, that's when you'll want to hit him with an accuracy & pierce-enhanced Cyclops, Minotaur, etc. Doing damage to Frostbranch with a low-pip, single-hit spell will remove the smokescreens and save you from his Efreet cheat. Repeat as needed, every time he smokescreens you. Meanwhile, use your turns in between to heal, set traps, and save up your pips for a higher level spell to finish him off. Once you have enough pips charged, then you want to put up a blade or two and hopefully take him down with a pierce-enhanced Medusa.
Another option is to save up a few crowns and buy a Fire Lion henchman (level 70). He can help you by doing some hefty damage on his own, plus taking a hit or two on your behalf. Or, the Life Gorilla (also level 70) does a lot of healing and will keep you alive long enough to win this fight. These two suggested henchmen cost 100 crowns each, and can really be a great help at your level.
Just a little trick for those enemies you have to hit every round. I use the sparklers from my wand. The hit is only 100 or 110, but it's a zero cast card, it lets you build your pips and it keeps him thinking you're armed. So in between your shields and blades keep him busy so he won't say "I thought you were here to fight."