[MENTION=9249]Viktyr Korimir[/MENTION], the only spells that clerics can have ready on the fly that healers can't are cure spells. As I pointed out, you rarely need more than a few of those for emergency healing during combat. And they get a number of status-reducing spells for free which lets them deal with virtually any situation on the fly whereas the cleric is the one who has to "guess" since they can't spontaneously cast things like remove paralysis. And 5 points is 5 points. Every little bit helps. And the companion is a bigger factor than you might realize. Not only is it an offensive tool, it can add an extra action to heal in combat. Anyway, its clear we both have our opinions and aren't going to budge. I've seen a healer played from level 1 to 21 though and it was a very effective character for a number of reasons. All we added were some healing-themed spells from other sources, which isn't unreasonable in a campaign where clerics get access to the same stuff. Perhaps you played in a similar campaign with a healer and saw otherwise, but I can't speak to your experience. I'm not going to argue that the healer is a better class than the cleric, because the cleric is clearly more versatile. But the cleric simply is not a better healer than the healer, leastwise not simply because of spontaneous healing.
[MENTION=52073]Eldritch_Lord[/MENTION], you should read a little further in the divine spell preparation rules. It says a divine caster need not prepare all of their spell slots at once. As long as they stop to pray for their initial spell slots at the intended time, they can prepare open slots later. But spells that have already been cast don't count as "open" for this purpose.
Anyway, OP, have you considered whether you really WANT to be a healbot? Some players enjoy that. Others don't. The healer doesn't get to do much aside from keeping fellow players alive. The companion is useful as an offensive tool, but probably not as powerful as a fighting cleric can be, given the time to cast the proper buff spells. Maybe just make the other players aware of the fact that you don't intend to be a full-time medic, and just plan to be able to heal between combats.