I was thinking about this and it seems a valid concern that monks are going to become glass cannons. As a remedy, why not adjust the stances to compensate?
General theme:
Earth stance should give good PRR and good AC (which it already does in theory)
Air stance should give good dodge (but nothing else)
Fire stance should give moderate PRR (combined with jidz should be decent)
Water stance should give good AC and good dodge
Specific implementation:
Earth stance does grant 0/6/12/20 Physical Resistance and 5%/10%/15%/20% AC.
Air stance could grant 3/5/7/10% dodge
Fire stance could give 0/3/6/10 PRR
Water stance could grant 5%/10%/15%/20% AC, 3/5/7/10% dodge
This keeps the stances in theme but gives some needed survivability. Honestly I don't understand the overhauls or the impact that some of the specific suggestions would have so if anyone wants to crunch some maths on what would be appropriate for each stance then be my guest