But what if you did a bonesaw + all defensive items build? Surely skaarf's damage could come close to a krul's with the same build, albeit definitely not his sustain.

Getting tornado trigger before you get another WP item is literally worse than getting a sorrowblade in every way (except it costs 500 less but who cares?). Also, what Zyronl said.

Why do so many people rush clockwork?

Buying clockwork first seems a little ridiculous. You could double your damage with shatterglass, but instead you choose to make cooldowns 33% shorter? Even if you need the energy, why not go for eve of harvest?

Has anyone considered buying two of these so they can sprint twice in a row?

Yes. Well, technically speaking it only means you get the passives from ironguard, meaning that you only get 12 HP regen on this item, not 15 like that would make it.

Alternative current if you have other crystal power items and they let you attack them for a while. Otherwise, definitely aftershock.

I would personally say yes for petal, no for skaarf. I think you should get frostburn instead on skaarf, so that your goop slows even more. But that's just my opinion, and I haven't actually played skaarf.

Taka doesn't get burst attack speed. Or do you mean when he buys items like tornado trigger? Either way, this is good if you are melee (so you can actually get in range to use it) and the enemy actually cares about their attack speed. If taka has only a tension bow and aftershock, he won't care if he attacks a second time, so this item would be useless against him. It's probably the most effective against SAW, since saw basically has to keep attacking you.

If you want defense in a long gruely battle, get fountain. It's almost twice as efficient as this, but it's stats are spread out between health, shields, armor, and health regen. If you want to block ulti's but there isn't much crystal power on the enemy team, usually get crucible. It gives you a lot of health, which is good against both weapon and crystal damage. Also its active is slightly better. But if there are 2-3 enemies using crystal power and you need to survive it, get this....