Diablo – What are the spirit-generating mechanics for Crippling Wave – Rising Tide

The tooltip is a bit misleading in this case. The only reason Fists of Thunder generates more spirit is because its animation is fast, which means you can use it repeatedly.

The thing about "on-hit" abilities in Diablo 3, is that there are very few static damage modifiers. Lifesteal is a %, and +damage is converted to % weapon damage by the skills as well. Hitting twice with Fists of Thunder will do 220% total damage, just like hitting twice with Deadly Reach (which also does 110% weapon damage). The difference is that you will perform two Fists of Thunder in less time.

As to how much faster Fists of Thunder is, that'll be hard until folks write tools to better read the game data, and it'll vary with weapon speed to boot. A slow weapon will mean slower Fists of Thunder (but still faster relative to other spirit generators with the same weapon).

The spell best suited for this is Shock Pulse with the rune Living Lightning.

The spell has an insane amount of hits/second, however each hit deals low amounts of damage , but it adds up to the same DPS as any other spell doing the same amount of weapon damage percentage.

Combine Living Lightning with items that improve Attack Speed and you will fire an insane amount of attacks per second, with each attack producing lots of hits/second. If you fire off several Living Lightnings, you will regenate 5 Flashes of Insight in a few milliseconds after you've casted your non-signature spell.

The skill: http://eu.battle.net/d3/en/class/wizard/active/shock-pulse
A video showing the skill in action:

They use Shock Pulse and Living Lightning with a rune that reduces cooldowns by 1 second for every critical hit. You gain lots of critical hits with Living Lightning without critical hit gear, imagine what you get if you gear up correctly!

NOTE: I am not sure the above build works anymore, changes were made recently, but Living Lightning was unaffected.