Path of the Damned is... surprisingly easy. If you find Hard difficulty easy enough then Path of the Damned should be cake walk for you too. I know the devs say they don't punish players for not specialising on any class (in fact you're encouraged to have mixed and matched abilities and talents from different classes), but as you probably know, some abilities prove more useful. The Leadership tree with its buffs is very useful, especially the "Undying" talent.

I've started as war mage in my first game, with heavy focus on magic and dual weapon fighter. But in the New Game +, I have focused more on magic but invested on the Leadership tree (it is in Path of the Damned I realised that Leadership tree is very powerful!). There is a general consensus that the mage class is the most powerful in Tyranny with the final talent in the Magic tree able to induce a powerful shock wave and almost always causes status effects on enemies. I and many players also find it easily that using spells that provide buff, particularly Haste and Mirror Image, is needed in the game to make tougher battles more manageable or easier. Sirin's Aria of Memories is highly recommended to have as the ability summons a ghostly image of Sirin that distracts the enemies. It is also best if you also train non-mage companions to also cast healing spells to make healing streamlined.

Those are the tips I could think of when playing PotD, which is surprisingly easy if you know what you're doing. But as I said, devs encourages players to experiment. So much so that the tips I gave, I figured them out on my own and I was surprised that many other players online have independently made the same observations and tips. Mage class is definitely the most powerful but I'm not sure about other classes and how they would do in PoTD. You could try and see how it goes! I might actually try specialising in melee next time!