Base cast time of regrowth is 1.5s
Base cast time of Healing touch is 2.5s
Current HT heals for 400% spellpower (increased by 15% due to artifact)
PTR Regrowth heals for 350% spellpower initial heal and 60% over time (increased by 15% due to artifact)
Protector of the grove causes your ht/regrowth to always crit and reduce cast time by 50% when cast on allies
Uncertain if this will reduce your GCD as well so 2 sets of data (this is mostly irellevant as regardless if it doesn't reduce your gcd, your haste will)
with 0 haste
assuming POG doesn't reduce gcd
(350 * 1.15)/1 = 402.5
(400 * 1.15)/1.25 = 368
and if pog does reduce our gcd to 0.75 then its
(350 * 1.15)/0.75 = 536
so its a 45% increase if GCD affected or a 10% increase if gcd not affected.
This math is also completely discounting the heal over time effect of regrowth which results in a slightly higher sustained heal over time and it is also a 2x nerf to mana efficiency, with Healing Touch costing 9% Mana vs 18.6% mana for regrowth.
This math remains the same as gear increases until healing touch approaches 0.8s cast time at which point it would have overtaken regrowth in HPS (however this would require an additional 45% haste)
TL;DR: Throughput buff to healing, sustain nerf to healing.