Hi,
No, I don't think it would be worthwhile to gear for spellpower in all areas. A main and an alternate seems like a good balance between convenience and being able to hit high spellpower values for the preferred primary imbues.
The fact that the AA secondary imbues allow you to bypass some DR also helps this situation too, because it could remove the need to slot augments for that purpose. Now that DR is a serious defence again in newer content, that ability seems more valuable than before.
Since potency boosts healing and all forms of spell damage, people who are more interested in convenience than power could get away with just that one effect. Maybe we will also start to see some new named bows which have potency, devotion, or elemental spellpower boosts on them.
Thanks.