As someone who plays acranist/summoner (or actually all classes if you don’t mind me bragging for a minute), I really want to empathize that you should not focus on healing as arcanist. Your job is that of a damage dealer for a reason.
As example: I have 80798 HP on lvl 80 with my summoner and casting physic heals me… 825 hp (or about 1225 when the heal crits). When it comes to parties let the heal do their job, and when going solo kill all the things before they can kill you.
Hope that helps.
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PS: If you are looking for a class that can hit things and heal themselves, you might wanna try out paladin and red mage.