i disagree. There is a buff icon, it is 10s and it matches the one you see in your abilities. However, if they are autoattacking or casting, they will probably not see it as it will be consumed. It works best when used with a dot as the damage on the dot is increased every tick. Try and group with a necro and have them use their dots with it. You would want to have a macro that tells your group members you are casting it BEFORE you do, like a 5 sec count or something. I use vent, so I just talk it out.

As for using chains, it does work. Pair up with another monk and have them jin surge your finisher. You can not jin surge your own as then your finisher is no longer available which is why I say to pair wih another monk.

As a Dragon monk, I love Jin surge in combination with Feet of the Fire Dragon... if it also crits, the damage goes up to 1200 per tick for four ticks, which makes it almost as good as the two fist finishers. I also use it when I'm tanking to grab aggro on multiple mobs, in conjunction with Whirling Storm / Dragon AE.

A hard number would be nice. It would also be nice if it weren't consumed on auto-attack. Don't know about reactions, though. That might make it overpowering. Imagine upping the damage on Thousand Fists...I would rather NOT see the timer increased and the use broadened to finishers (because that's probably how the devs will see fit to balance said change).
I do not need another "use once then forget" ability. It's bad enough there's Pushing Hands, Waning Palm, Goading Slap, Dragon's Rage, Cloud Dragon's Ruse, etc which all have limited to no use.