No offline option as of now. But they will be adding single player story campaign soon, you can see that in the official video trailer on 1st pageLooks like new cards being added to deck...
can we play it offline ?
I'm also playing this casually. But it's good.They have nerfed some features. The artillery line has been removed and artillery cards go on the ranged line. I also found the meta to be somewhat hard since you can have a lot of cards in your deck and too many attributes to keep track of. So, I only play this casually.