Skills for an Inferno hero.

In my opinion, Hellfire is only really helpful at the beginning, and by the middle and end of the game, even with Withering Flames and Fiery Vengeance, it becomes less relevant. It also depends on luck; instead of a 100% chance to deal extra damage on attack, you'll have a 30% chance to deal 150... is that really critical? Isn't Battle Frenzy more useful?

I wouldn't max out Chaos skills just for a 10% damage boost; it's not worth it, IMO. If you really want to, you can max out the Ice Lord skill in Chaos and Cold Steel in Attack, which gives you the same 10% damage boost, but without the crazy investment in Chaos, which isn't very useful for a demon. I rarely max out Hellfire; its usefulness is questionable, and Withering Flames doesn't really help. But Battle Frenzy can be extremely useful, not so much for demons, but very useful for Necropolises and other numerous factions.