Ball lighting (since it is slower +.02)
155 to 310%
Ball of lightning is one of the strongest skills in the game at times. It has huge area and will hit massive enemies considerably more than the average used to compute the tooltip. Attack speed also seems to make it hit more often during the flight on top of allowing you to shoot it more often. When thrown into missile dampening even a few will kill any stationary elite as they will give off hits for well over 10 seconds. The cost is also low enough that with a bat and regeneration gear you can stand shooting it off for quite a long time. There is a reason why it is one of the most used Demon Hunter skills. Let us not forget the added bonus of life steal applying when it is fired so even if shadow power expires it will keep stealing life for the duration.
With your proposed buff it would become crazily powerful. Anything massive would be trashed effortlessly and anything with missile dampening is even more of a joke. If you buff damage like that you will need to nerf area a tad so it is more comparable to the other skills and less prone to multiple hitting the same target.
Strafe 12 hatred to 10 hatred
156 to 281%
Strafe is already strong enough. With a decent 60k DPS find build you can face tank everything in MP2. As long as strafe is active, it will life steal at the rate you had when cast. This means all you need to do is cast shadow power once and you can have near indefinite life steal as long as you have the hatred (which you can easily get permanent strafe builds). Raise damage to the 150k area and you can plough through MP3 killing stuff without ever stopping moving. Let us not forget you can use skills like fan of knives without interrupting strafe for when you need that extra damage.
If damage was to be buffed like that you would need to make each shot check life steal to encourage the user to blow more shadow power (discipline) or to raise hatred cost a tad so maintaining it permanently is not as easy.
Multishot 30hatred to 22 hatred
165 to 267%
rune-full broadside 215 to 410%
It is already a highly usable skill. In low monster powers you can flash down virtually every high density white mob with a single shot. I agree that a hatred reduction cost on the normal variety is needed and that a tiny damage boost would be ok but adding nearly two thirds more damage is too much in my opinion.
These are all highly used because they're the best we have... doesn't mean any of them hold a candle to monk cyclone, or wall of light. Even the dh "nukes" like cluster arrow are doing 1/4 of what wall of light does.
While BL is the most used skill now, all of our spenders need buff, just in different amounts. I would say bring cluster arrow close to at least 600% and elemental arrow buffed only slightly (say 210%) this way there would be a reason to use cluster arrow, but BL won't become !@#$ in comparison. Other spenders should follow in a similar fashion.
I put some of my dh gear on my monk and she breezes through mp6 with only 400 AR due to lack of OWE. That entire monk is worth about 2mil at best while my dh is probably near 100 at this point.