Quite bluntly, it's not easy to get access to divine spells anymore. The Priest only gets domain spells, and even then, has a very limited usage of them. He also gets certain additional abilities which he uses to supplement and augment his spells, but by and large, his spell choice and usage is more limited than a Cleric's.
On the larger scale, the primary thing I have done to avoid this problem is:
a) extremely limited access to such combinations, and
b) limited character's resources so that if they DO decide to set up such combinations, that it will pretty much define the character.
The Priest is going to be the primary divine caster, the chassis for which 90% of all divine classes will be based on. You may wish to try to 'trick out' your ride for racing, but if the chassis cannot handle the load, the attempt is not going to be successful.
The other divine classes are going to be Crusader and probably something akin to a Marshall-esque 'paladin', with more a focus on divine augmentation than spellcasting.
Also, to address magical items, I'd like to point out that the campaign world is a *VERY* low magic item world. Quite bluntly, there aren't any wizards able to produce them anymore, so any magic items are either created from specific and specialized classes (Beguiler, Dread Necromancer, Warmage), with access to specific and specialized spell lists, or are pre-apocalyptic artifacts which cannot be duplicated. A +1 sword is a significant find. There are no more iMagic shops where you can simply download your 'wand of Win' app and use it indefinitely.
Does this answer your question?