[QUOTE=CyberNinja]My question, after all that digression, is whether or not there is something about the class I've overlooked, especially in my application of battle tactics? Is there a way to utilize the combination of magical might with melee capabilities that I have not hit upon?[/QUOTE]
That's an interesting question. You've already determined two important things: 1) you are playing a with a well-rounded, full party of six (as opposed to playing a solo character), and 2) you want your Fighter/Mage to be primarily a buffed-up melee warrior. Here are some suggestions.
First of all, you should let the rest of your party play specialized roles of their own while you let your Fighter/Mage concentrate on what he does best. For example, Nalia can cast spells that will dispel your enemies' protection spells while your Fighter/Mage is battling their minions. She can also cast crippling spells against your enemies such as Greater Malison/Glitterdust/Emotion (one of my favorite combinations) and Hold Monster. Nalia will also be casting massive-damage-inflicting spells, especially later on when she is high in level. Jaheira can also cast crippling spells against enemies at higher levels, such as Insect Plague and Nature's Beauty. She can also cast some nice summoning spells. Viconia can cast protection spells such as Chaotic Commands, Death Ward, Free Action, etc., as well as buffing spells of her own such as Draw Upon Holy Might and Righteous Magic. She can also cast offensive spells such as Glyph of Warding, Hold Person, etc. and summon Skeleton Warriors with Animate Dead. You'll need True Sight or True Seeing against a lot of opponents, and that can be cast by Nalia, Viconia, or your Fighter/Mage. Your party is too in level to do much more than they are already doing, but just give it time and make the most of their new spells as they become available.
As you know, your Fighter/Mage can buff himself up before a fight, but he's only 10th/11th level right now, and you ain't seen nothing yet.
If you have Throne of Bhaal, he can do some interesting things when he gets High Level Abilities, such as combining Energy Blades with Critical Strike. (A lower-level version of this strategy is to have a Blade cast Melf's Minute Meteors in combination with Offensive Spin.) Spells like Simulacrum and Project Image will let you create clones that can do amazing things. As for buffing spells, Spell Immunity is necessary at higher levels since there are enemy Mages who will rain on your parade if you don't counter-act the spells they will use against you. You can cast more than one Spell Immunity at a time, to protect against Dispel Magic (Abjuration), death spells (Necromancy), and True Seeing (Divination) at the same time. For example, if you cast Stoneskin and Improved Haste, Spell Immunity Abjuration will prevent an enemy Mage from slowing you down. If you cast Improved Invisibility, Spell Immunity Divination will prevent an enemy Mage from seeing you. I suggested Spell Immunity Necromancy because Fighter/Mages might be vulnerable to enemy spells such as Wail of the Banshee, Finger of Death, etc. because they will be targeted at close range. You might play around with Spell Trigger and Contingency later on. Contingency can automatically cast Stoneskin when you're wounded, for example. Spell Triggers can be used to cast area effect spells on
yourself to target all of the enemies who are surrounding you--other people can describe things like that better than I can.
The guidelines are pretty simple: increase resistance to damage (Stoneskin, Mirror Image, etc.), make yourself harder to hit (Improved Invisibility, Mislead), increase your number of attacks (Improved Haste), make your attacks do more damage (Strength potions), increase resistance to non-melee damage (various protection spells and potions), prevent enemy mages from dispelling your defenses (Spell Immunity), and make clones of yourself (Simulacrum, Project Image).
When you think about spells, think about combinations and try to make your spells work together to create an inpenetrable defense. By the same token, try to use combinations of offensive spells like the ones I've mentioned. Greater Malison and Glitterdust can really soften up your enemies, so I like to cast them before I cast spells that allow saving throws. At lower levels, Emotion and Hold Monster would work great for you.