So a healer is important I gather. How important is the magical "oomph" as mentioned. By group rarely gravitates toward arcane classes. But perhaps this is a game were it would be a good idea?
The major benefits to having a spellcaster in the party, in my experience, really start to kick in once you get past the lower levels (e.g. level five or so). By "spellcaster," I mean someone on a full-progression spellcasting trajectory (i.e. they'll end up being able to cast 9th-level spells).
Part of the reason for this is that spellcasters, especially preparatory spellcasters (i.e. wizards and clerics, rather than, say, sorcerers) are at the top of the
tier system, meaning that they have the broadest range of potential options to deal with various situations. A fighter will be reliably able to hit things, and a rogue will be able to use more skills than anyone, but a well-prepared wizard will be able to
charm enemies,
fly past them (while
invisible), paralyze them with
hold person,
summon something to harry them, and that's just with the low-level spells.
Now, a lot of this depends on player preparation. A wizard is going to want to take full advantage of their free Scribe Scroll feat in order to have a lot of "once in a blue moon" spells prepared (e.g.
water breathing), and should take every possible opportunity to expand their spellbook (paying careful attention to the rules and costs for scribing more spells) - including buying access to more spells whenever the party is in a town, city, or other settlement - which is a lot of work on the player's part. Clerics have it a little easier, as they have access to their entire spell list, but unless they take an item creation feat, they need to be highly judicious with regard to what spells they pick at the beginning of each day.
Item creation feats bear special mention. While non-spellcasters can take
Master Craftsman in order to make magic items on their own, spellcasters are still the go-to insofar as making magic items goes. The value of this can't be overstated (mostly for Craft Magic Arms and Armor as well as Craft Wondrous Item), because it lets the party customize their gear even beyond what the ubiquitous magic item shops will allow for (and you can
make items for half the cost of
purchasing them, hence the section on
magic item creation in
Ultimate Campaign). Given the importance of what magic items each character has, the value of this cannot be overstated.
And, of course, divine spellcasters have the ability to remove various afflictions beyond hit point damage. That's not
too common, of course, but there are things that a wand of
cure light wounds can't handle. You'll want to be able to ditch ability damage (or worse, ability drain) and negative levels as soon as possible, for example.
Overall, because Pathfinder is a high-magic game system (being patterned so closely off of D&D 3.5), it's really a matter of taking advantage of what the system allows for, especially since the higher level you are, the more the game assumes that you're already doing this, adjusting its challenges accordingly.
