Kinda. Don't forget mastery boosts DA - with ~13 mastery you get a 40% DA proc. Also the DA proc is calculated from the crit amount, not the base heal amount.
Currently:
10k poh procs 4k shield. Total non-crit = 14k.
15k poh crit procs a 12k shield. Total crit = 27k.
In 4.2:
10k poh procs 4k shield. Total non-crit = 14k.
20k poh crit procs a 16k shield. Total crit = 36k.
So poh gets hugely boosted on crit with this.
Other heals also get bigger DA procs, but not to this extent.
For GH, your 30k heal with a 45k+18k crit becomes a 60k+24k crit.