RE: Other classes you mentioned....
1. The Mage Blade:
Considering that the only healing magic available within your set-up is from the Dragon Shaman's limited capacity, and your Fast Healing bardic music addition, the Mage Blade seems out of place since it would be able to cast the Battle Healing line of spells, the Transfer Wounds line of spells, and even spells like Raise The Dead.
Assuming, of course, that you don't just ditch the Mage Blade's spell list from Arcana Unearthed and replace it with the Sorcerer's or somesuch. Although AU has weaker healing/rezzing spells in general, they are nonetheless much more significant than the other few bits of healing magic you've otherwise included in your set-up (well, aside from the possible unlimited healing your Fast Healing bardic music could do, through one or several BM uses in a day, if you aren't careful about how you detail the mechanics of that ability).
If you do keep the Mage Blade's original spell list, then you'd likely have/want to include the Complex Spell and Exotic Spell feats from Arcana Unearthed; but then, since you plan on including the Champion too, I figure you'd likely be including at least the feats listed in those two class' Bonus Feat selections.
Also, a note, the Mage Blade is kinda underpowered if using the spell list and such from Arcana Unearthed, since they have 'Multiple Ability Dependency' like Monks, Paladins, and Psions (at least the Psions of 3.0E). The standard Mage Blade uses Charisma as their casting stat, but has poor HD and BAB for a frontline warrior-mage class, so they need good Str and Con as well (or Dex and Con if using a finessable weapon), and they lose some of their extra mobility if they don heavy armor, so Dex is a little important too...... Plus there's not much for a low or mid-level Mage Blade to do about beefing up their AC spell-wise, thus the added usefulness of good Dexterity.... Some of these things are less significant though if using the Sorcerer spell list or something, as opposed to the original spell list in Arcana Unearthed. I would still probably recommend making Mage Blades Intelligence-based casters though, or possibly Wisdom-based. Charisma doesn't really help them much, except with their spells (and, as a note, many AU spells require attack rolls rather than allowing saving throws).
2. The Wizard:
Yes, give them a d6 hit die. Without divine casters or spellcasting bards around to heal and buff the fragile wizard, he or she is likely to die very quickly if not thrown a bone of some sort in the self-preservation department. Mage Blades with the AU spell list don't really suffice for this purpose, as they don't have much to heal/buff a fragile teammate very well, at least not at lower levels.
3. The Spellthief:
You'll almost certainly want to beef up the Spellthief a bit in one way or another. With the reduced variety of spellcasters around (and thus reduced variety in spells available in the setting), combined with its already-existent bit of weakness, the Spellthief could probably do with a boost to its base skill points, hit dice, or something.
4. The Shaman:
You could base your concept on the Shugenja printed in Complete Divine (and before that, Oriental Adventures for 3.0E). Remove the relatively-few non-elemental spells from the Shugenja's spell list as appropriate (such as the Cure X Wounds spells that belong to the Water element spell list for Shugenja), shift a few spells from the Shugenja schools (I forget what they're called in CD, I think they were called 'orders' or somesuch) into the appropriate elements of the main Shugenja spell list, then replace the Shugenja schools/orders/whatever with Totems, granting whatever benefits, abilities, or extra spells known that you intend the Totems to grant. You might remove the Sense Elements class feature as well depending on how potent you make the Totem benefits (shugenja can basically sense the presence of particular elements nearby, such as sensing sources of water (including living creatures of course) within a few dozen yards.
See, Shugenjas each have to choose an element to specialize in; either Air, Earth, Fire, or Water (you could add further elements if desired); and they have to choose a school/order to learn their magic from, which simply grants a set of extra spells known (1 of each level, including 0-level, similar to a clerical domain but with no granted power). The Shugenja is normally a divine caster that receives their spells from elemental nature spirits, but your version could be arcane instead. They're normally Charisma-based casters (though changing it to Wisdom-based would make at least as much sense in-game, really), and spontaneous. Number of spells known and per day resemble the Sorcerer's spell progression.
Shugenjas receive the benefit of Spell Focus with all shugenja spells of their chosen element (can't remember if it stacks with the actual feat or not), but this is their only benefit from their forced specialization. Half the spells they learn are from their chosen element (plus the extra spells known from their school/order, but that's very limited), and the rest of their spells known must be chosen only from the elements not opposed to their own (Air Shugenja can't learn Earth spells, frex). Each element on the Shugenja spell list has around 3-8 spells of each spell level (excluding 0-level, which has only about 1-3 of each element). Most shugenja spells are purely elemental (some are just thematically appropriate though, like teleportive spells amongst the upper levels of the Air element, and healing spells amongst the upper levels of the Water element, etc.).
The list also has a few spells at some levels that are considered to belong to all four elements (and thus available to all Shugenja who choose to learn them), such as Scrying, Protection From Elements, Summon Nature's Ally, etc. Though, Shugenjas are limited to summoning only basic Elementals (i.e. air, earth, fire, and water elementals, not just any creature of the elemental type) with the Summon Nature's Ally spells.
Alter the Shugenja's name, elements, class skills, proficiencies, etc. to suit your idea, and there you go; at least I think it would be less effort to adjust the Shugenja than to cobble together a new class. There shouldn't be too many name/element/skill/proficiency changes needed, thematically.
: Elven magic empire, uncivilized land for nomads, a stripe of many small Dwarven democracies, and Hobgoblin socialist empire. In between are Human theocracies or democracies and at least one nation made up completely of Gnolls and a Vampiric subrace of Elves. In this setting, at least on this continent humans are not the most successful or expansive or technologically advance race, but play a role similar to Halflings or Dwarves in other settings.
