I use it because late game, 4 second cd on warp strike is really good, and it's easier to get more spines off quickly in fights.
I suppose that could work, but I feel it would just leave you way too squishy early. No BoTF for staying power. No HW for leveling. I'd just think it would make you far too weak to be of much use early/mid game. + with the mana costs of his abilities, being able to spam them more often doesn't help you at all early or much mid game.
You say that evasion is bad, and I agree. If you don't think it's good early, do you think it's good later?
I don't personally think its good late either. Sure, there's going to be a bit more AA late game, but the vast majority of damage is still going to come from ability damage. The only place I think it might bear some value would be against minions. Anyway, I still don't think its truly worth it.
re: demon speed - sure, that can definitely be fun. I fit that in when possible. I think the bottom line is that the ability sequence you choose should reflect how you play and not some dogmatic approach. For instance, I generally don't use my abilities unless I have a very good reason or am going for a kill. This means that early game, maxing warp strike and spine attack is fine as I will likely have enough mana available when I need it. That said, if I didn't have the mana, it wouldn't be quite as valuable to have those maxed earlier than later. So, I really think it comes down to play style.
I'm still not a fan of staff of renewal on da, but if it works for you, then great. I just think you'd have a good deal of difficulty early/mid and perhaps even late game as you are very likely going to get outleveled and pushed out if you are the solo lane guy. I pretty much treat playing da as a rush to level 15 - if I make it there before anyone else, well - folks are going to die alot. That's why I like hw so much on him. Because even if you screw up and get pushed out of a lane, you can still farm your lane from base.