To be honest making the ingredients rarer or in hard place will not fix possible balance troubles. As someone said before, there are still some people (invidually, or in well organized groups) who will manage to get them and hoard them. And Greater Restoration and Heal are way too strong potions to have around in large numbers. I'm fond of the crafting system of POTM, but giving so much power-related possibility to the easiest (i.e. less expensive, with lower DCs compared to others, and with most materials, even for powerful items, really way too easy to obtain) craft around is going to unbalance many things in the short, mid and long term (dungeoning, dm events, pvp).
I hope the developing Team reconsiders the hypothesis to have them in game as craftable, a rare loot (such as hector's essence or tenser's transformation potions) would be better fitting.