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).
I finally got this rune, and tested it out.
I can confirm that effect is triggered, and that it will trigger off of large groups of normal monsters as well as bosses and elites, although it seemed to take more than 5 monsters before the effect was triggered. Exactly how many more I could not be certain of, because the monsters were already dying by the time I saw it trigger.
It seems to attack quite a bit faster than normal, so I'd say the 35% attack speed is a 35% bonus, rather than 35% of normal attack rate.
His damage appeared to be roughly 3x normal (I was seeing hits with the buff around 300, with crits around 450, and hits without the buff were in the 75-125 range), so again, the "200% Physical damage" appears to be +200% additional damage.
The buff lasts about 15 seconds.
All in all, this is a pretty nice buff.
Best Answer
There isn't any. The only indication you will see is a slight DPS boost in your character sheet for a few seconds.