Min/Max Boards

Maze would work, if the character failing the int checks isn't unreasonable.

I seem to recall a story about a runecaster doing something similar.

http://www.minmaxboards.com/index.php?topic=6804.msg108662#msg108662

Well, it was an arrowsplit rune, but I think that might add an additional degree of effectiveness for the crossbow.  Maybe a Gate rune so it doesn't shoot swords, it shoots a crossbow bolt and a pit fiend.

What's your target, starting level, etc?  Could be there's a different way to do what you want to do (Rainbow Warsnake / Weavermage comes to mind http://www.minmaxboards.com/index.php?topic=1473).

http://community.wizards.com/go/thread/view/75882/19535398/Best_cleric_domain  Here's a collection of some -good- domains to pick up.

http://dndtools.eu/feats/complete-divine--56/arcane-disciple--92/  Here's the exact text.  Pick a deity and you can Arcane Disciple yourself a domain.

Improvisation.  Best bard spell in the game, if you're not using it you should.  http://dndtools.eu/spells/spell-compendium--86/improvisation--3531/  Bard1, improves with caster level, works for your attack rolls and skill checks (for stuff like tripping this is great).  Something to throw down at the start of a combat as you move to close.  It's also cheap, flexible, and no gm in their right mind would say it's overpowered (unlike bladeweave, lieber gott).  Very very useful.

Another vote for bard/SC or buffer wizard that goes into War Weaver.  Bard also has the fun little trick of being able to be king of all the obscure skills (Jack of All Trades + Bardic Knack).  Bit of spotlight, helpful bonuses...and you're a bard, there's a lot of fun story options with that one.

Improvisation.  Flexibility.  Having a living world rather than a static plotline or a flowchart--both of the other times my brother tried a flowchart to GM we ended up going outside of planned contingencies. 

(One case was my Jedi going door-to-door like a cop looking for someone who didn't show up to work for a senator that day, thinking that he'd find the assassin he'd been advised about trying to impersonate them or find a body or something.  The other involved attempting to talk our way out of an encounter with a Sith 6 levels up on us instead of fight our way out.)

Can they keep a handle on everything?  Battlefield status, character status, opponent status?  Running an encounter's a lot different from fighting one.  Has either of them been the party leader-type?  Not necessarily the face or the BFC, but the one ultimately dictating where people went or what happened.  That personality can be useful to have running a game.

Useful party buffs.  Show the bard all the Inspire Courage tricks http://brilliantgameologists.com/boards/index.php?topic=9830

Lingering Song Feat (Complete Adventurer 111): Your Bardic Music lasts for 1 minute (10 rounds) after you stop performing instead of 5.

Song of the Heart Feat (Eberron Campaign Setting 60): +1.  Other feats get bonuses too, but those don't matter for our purposes.  Nyah.

Eberron Campaign Setting 34 states a Bard may take this feat in place of a new form of Bardic Music at level 3, 6, 9, 12, 15, or 18.  Since these are "bonus feats," you can debatably skip the prereqs.  If you can, then in short, you can dump Inspire Competence to take this and, say, Dragonfire Inspiration at level 3.

Words of Creation Feat (Book of Exalted Deeds 48): DOUBLES your Inspire Courage bonus with any instrument.  Saner interpretations say this is only from levels, but RAW says 'doubles.'  You also take icky subdual damage unless you're immune.

If the whole party hits and does decent damage, you don't outshine them as much.

You could tweak the crusader to go for more lockdown and play more "setup" with the druid.  Remind the rogue's player about sneak attack (if you're deliberately setting up a situation where your opponents are blinded/flat-footed/stunned/otherwise vulnerable, it looks good, especially if you can come up with some kind of in character reason to serve them up like that). 

Mention to the guy with the wizard that he can use a spell to do Xd6 damage or he can use that same spell level to, say, grease an enemy and give the rogue a bunch of d6s on every attack.  If he wants to do damage, there's lots of very nice ways to do that, more frequently by using other people.  My last game ended because my brother's dervish was just too efficient a delivery mechanism for my bard's well-honed Inspire Courage ability.

Or point the wizard guy at Mage of the Arcane Order taken via sorcerer (arcane preparation).  Cast "basically every spell if you want", and yet still have a focus you're very good at.  Or the Rainbow Warsnake if you think the game will get that far.  Because if any spell on the cleric list any time you want isn't enough spells, he's doing something wrong.  =P
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Let them be what they want, but just offer the options and relax a bit.  So long as they're not actively being a problem, you can always go beast mode and "win" the encounter, keep the panic button in your back pocket.

DR, miss chances, being out of range...glaring easily exploited weaknesses of individual spells is why you grab a little from column A, a little from column B.  The metamagic feats that have the best overall coverage, the spells that (together) cover the most things.
But yes, for underlooked spells it's definitely a very nice trick.

It's easy enough to see how you might get encounters one CR lower.  Attacking a bandit headquarters?  Smith and Jones have pegasus flu, so they can't guard the room, leaving just Johnson, Jackson, Sanders, and Baker.  There's lots of different ways for the CRs to drop.

One death every two and a half levels.  Given you're (theoretically) supposed to have 13 encounters/level (yeah, right), that's...around 33 encounters.  A 1/day reroll and only failing the save on a 1 would get you 1:400 odds. 1/33 is easy by comparison.  A 1/day reroll and failing on 1-3 would get you around a 1:36 chance of dying...if I'm running the math right.

http://www.minmaxboards.com/index.php?topic=3472.0 This might be a good place to start.  There was a post a while back that flight was expected by ECL5, the ability to deal with grapplers by ECL7, reach by such and such a point...just the trends.