You're right that it's hard to have decent mana regen without Meditation, especially for long battles. However, I find that if you're running out of mana on anything shorter than a five minute battle, either you're not using the most efficient spells for the task at hand, you're overhealing, or you're not stacking enough spirit. Something I learned the hard way: All the +heals (or +spellpower, now) in the world won't help you if 15 casts is all it takes for you to go OOM. Give up some of those +12 Spellpower gems and put Spirit gems there instead.

Are you remembering to set your shadowfiend out *before* you're out of mana? If you balance things just right, you can find a nice chain for especially long fights: I use my fiend when I'm around 40%, which usually gets me in the 90-100% area, pop a mana pot around 60%, again at around 30%, and can usually use my fiend again before I'm OOM, bringing me back up to around 60-75%. Of course, depending on how heal intensive the battle is, you can take turns with the other healers in taking a break in casting to allow regen, before you're tapped dry. Bangle of Endless Blessings or Earring of Soulful Meditation are both very helpful with this tactic.

I can't compare druid regen to my own, but I find that if even with all this, if you're still pushing it to the limit, and running dry before the battle is over, make friends with the Druids you run with (especially feral!) and stack spirit. In a tight spot, give them notice that you may need an innervate, and when they find a moment, they can send one your way; with enough spirit, you don't even need to stop casting to go from bone dry to 100% mana. If you're low on spirit, one of the trinkets above can be popped just before you are Innervated to boost its effectiveness.