Tiger - two-handed.
Don't really use other stances, but they are more fist-friendly.
Of course, in the later game, it's so much easier to get a decent two-hander (DT and Graystone both has heroic martial staffs) than to get two decent fistwraps. Don't know about the level 50 areas though, but the 72.something DPS staff from graystone is hard to compete with in Tiger stance, very hard. ~
I don't play by macros, but it is doubtless more efficent (however, I have a feeling that changing weapons will occur a global cooldown sooner or later, so the more comfortable you get with it, the worse feeling when it's no longer possible).

That would be because crance stance doesn't effect the dex dodge and parry,  you have to hover over the Defense rating to see it be effected by crane.
and to answer your question
No crane is not broken
Harmony stances are working fine,  although Harm body stance probly needs an increase in jin regen  but its better then a none functioning dragon's regen stance.

Try mousing over your defense stat and you will definately notice your evasion go up.  Also if you mouse over the buff icon for crane stance you'll notice its more like 8%.  I think the 20% on your stance bar is an artifact from before the evasion nerf/fix.

As far as weapons go... i was purely 2h with tiger stance a few days ago but lately i'm noticing the difference in crit between duel wielding and using a 2h in tiger.  I'm still not sure which to stick with but its hand to hand in tiger for now.  And i just drag my weapons on to my hotbar for the time being. 

Just an update for everyone, on the original topic:

I've tried it for two levels now, and as a harmonious monk I seem to have a much harder time maintaining agro of single mobs and groups when duoing with a disciple than as a dragon monk (level 18 and 19).  I suspect it is the slower attack rate of the two-handed weapons, and the lack of weaknesses I can exploit that either I or the disciple could start.

So, last night I switched back to dragon monk.  Harmonious might be better than dragon monk at higher levels, but in my particular situation, I can do more damage more quickly and manage agro better for our duo as a dragon monk.