IMHO those are two of the best schools to combine. Healing spells do not scale off of int, same as summons, so someone who is your healer / summoner not only gets enough to do to actually use all their AP, but also is still the most stat-flexible you can get. Sure you may be tempted to stack Int so you get more mileage out of the few damage spells Hydrologist and Summons have to offer, but it's not the only choice, you can also absolutely load up stuff like Con and Memory and have all the spell slots and health you could ever want, having a healer / summoner that just won't ever die and always has spells to cast. Their actual in combat efficacy wouldn't even be hurt much because honestly, if they always have summons and heals to cast, how often are you really going to have the AP for their damage spells anyway?
