I think more paragon classes and the like in future books will help add variety, which will be nice. At the same time, the "three class choice-points" of the class + paragon path + epic destiny system will keep things from getting out of hand, I hope.
I've posted something like this elsewhere, but I'll say it again: I was originally kind of "blah" about the multiclass stuff, but then I started looking at things in more detail. The key thing to note is that if you go the "full multiclassing" route of taking the multiclass paragon path, you now have fully half of your non-utility powers from your second class.
Yes, HALF.
If you take all of the multiclass and power-swap feats and choose a paragon path from your multiclass, half of your powers are from your base class, one quarter from your second class, and one quarter from your paragon path. (So again: half and half, more or less.)
So, what's missing? The special class-based abilities, basically--but that's all to the good in terms of "if you are a wizard you are always a wizard first" model. If you go full dual-class, and are a fighter/wizard, that's different from being a wizard/fighter.
Let's look at this for warlord/wizard, since they can have some good common stats more easily. Int is the clear first choice, but we'll also need a high strength to hit with most warlord abilities. In addition, charisma opens up some options for the wizard, and has benefits for the warlord.
The warlord/wizard is a warlord first. What can he do that the wizard/warlord can't? Well, his abilities are combat leader (+2 to nearby allies on initiative), commanding presence (tactical presence) (+1/2 your int mod on allied attack rolls when allies use an action point to attack), and Inspiring Word (allied spend healing surge +nd6 2/3 times per encounter.) (The other character can only use this once a day.) He also has some pretty powerful controller abilities, but he's first and foremost a leader.
The wizard/warlord is a wizard first. What can he do that a warlord/wizard can't? Well, the war/wiz can use implements when casting spells, but he doesn't get implement mastery. So the wiz/war gets the benefits of an implement mastery (probably orb, so he can reduce an enemy's chances to save or extend the duration of an at-will with a duration once per encounter.) He has access to cantrips, which the war/wiz does not have (so he can, for example, create light with a wave of his hand, and the other cannot). He automatically gains ritual casting, whereas the war/wiz would have to spend a feat on it. And the most major thing is: he has a spellbook. At level 20, the war/wiz has two daily wizard powers, and two wizard utility powers. The level 20 wiz/war has his choice of two of four daily wizard powers, and three of six wizard utility powers.
So: Are these really "dual-class" characters? I would have to say yes. They really partake a very large amount in the "schtick" of the other character. They have traded fully half of their powers over, and can function tactically in both roles (to a certain degree.) However, the original choice of class has serious ramifications. The warlord/wizard does not have the daily flexibility of a wizard, the specialist bonuses from implements, or the basic cantrips. The wizard/warlord lacks the ability to improve the benefits his allies gain from action points, and cannot heal.
Whichever way you go, the base class determines the role your character performs best at. However, the second class certainly does change things a whole heck of a lot. You can't say "yes, I want to be equally good at both of these things", but as I see it, that adds to your options, it doesn't detract from them. As we've seen above, the two choices are radically different from each other. They both have their strengths and weaknesses. Neither one is merely "dabbling" and neither one is a bland balance of the two that has no identity of its own. That's great! And if you do want to dabble, well, going the less radical just-power-swaps is great, too.
Moving on to the paragon paths for these two:
Warlord/Battle Mage: Some very awesome possibilities here. The Battle Mage specializes in being in front--the warlord is already there. Elemental opportunity attacks with + Int modifier in damage. +4 bonus to attack roles when you use an action point. Free use of any at-will when bloodied. Some nice burst damage powers and a "save my ass" power which is sure to be a winner, keeping allies from having to save you with a potion before you can save them. Flavor: This character has studied the arcane arts, and then focused their attention purely on how those arts can aid them in the front line of battle. They lack the full repertoire of a serious wizard, but their support abilities in combat know no peer.
Warlord/Blood Mage: The general idea of the blood mage seems to be someone who adds power to his spells using his own life energy. This doesn't seem to be a great fit for a multiclass, but could be challenging and fun. Your ability to heal yourself makes the spending of health and healing surges less of a handicap than it might be for others. On the other hand, that's kind of "weird" flavor-wise, and also means you have to waste time healing yourself instead of being bolstered by an ally. I'd personally not play this combination as a war/wiz. (A lock/wiz, on the other hand, I might... Could also be good for a ranger or rogue.)
Warlord/Spellstorm Mage: A weather-themed path that seems focused primarily on damage-dealing AoE and area denial effects. (The draw-a-spell-from-the-spellstorm looks most useful to me to allow a bit more staying power with the big-hitting powers.) This would be a better fit, I think, for a cleric multiclass, because of the wisdom emphasis. However, the ability to control areas could be very very nice for a warlord--more ability to control enemy actions to back up your ability to bolster allies. I'd consider trying this, although I can't think of a good fluff reason for it right now. I can think of a good fluff reason for a cleric, and I'd really consider doing that one.
Warlord/Wizard of the Spiral Tower: Spellswordish. Like the Battle Mage, this is an awesome fit for the warlord. You can use a longsword as an implement, so no more pesky sword-in-one-hand-orb-in-the-other. The ability to use an action point to regain a wizard encounter power extends your staying power with wizard powers, which is great. Enemies that attack your will take damage based on your charisma, which is very very awesome. Great mix. The fluff here is that instead of focusing on weaving arcane powers into your battle strategies, you have woven them into your swordwork and your willpower directly.
So--two great options which are very flavorfully appropriate, one which might work okay with the right focus (although a bit too many stats involved at that point), and one which is really not a very good fit at all. And all of them quite distinct from the pure multiclass model, which is also good.
On the wizard/warlord side:
Wizard/Battle Captain: This is focused very much on group support abilities and battlefield control. Not a bad match at all. Taking this paragon path allows gaining some of the power that a pure warlord would have in terms of inspiration, including boosting action point usage and the ability to return a power to an ally. The remaining powers provide battlefield control through movement, which fits right in for a wizard. Fluff-wise, this wizard has studied the arts of war and is able to provide very insightful leadership on the battlefield. I'd probably fluff up the warlord attack powers that move enemies to use a mix of martial and arcane forces rather than pure weaponwork.
Wizard/Combat Veteran: The combat veteran is similar, but with a more hands-on focus, and features more "toughness" than the battle captain. This is not quite as good a match, since it seems to be predicated more on being in the front lines. But it works. Fluff: This is a wizard who's Been To War. He knows what it's like on the battlefield, and he knows what it takes to survive. When he uses his spells, he uses them directly and for effect--not to show off how he's a spell-slinger. In fact, he probably avoids revealing his nature as a spellcaster until he's forced to do so--he knows they're a prime target. But when he does throw out that fireball, he makes it stick, and he's able to stay alive after. (On reflection: That's a damned awesome concept, right there.)
Wizard/Knight Commander: Woohee, this one is kind of rough. To get this, the wizard also has to become proficient with heavy armor. That means he needs to spend two additional feats right there. That's kind of rough. (Of course, he doesn't have to get all of the power-swap feats before taking the paragon path.) Anyway: This is a much better fit for a defender-type, I think--either a defender multiclass or a warlord who wants to occasionally fill in as a defender. I can't see much reason for this except pure role-playing reasons (you've been knighted, and you feel you should do what's expected of you? Not a very good choice, I'm afraid. Your life expectancy is low.) Then again, the knight in shining armor popping out a Burning Hands could be a bit more than the enemy was betting on. Definitely want a high cha to pull this off.
Wizard/Sword Marshal: Also a somewhat poor fit, and requires a feat. This would be for a wizard who wishes to have more overall power with melee abilities. The one shining thing here is the Sword Marshal's Boon, which will allow the wizard to buff himself at useful times. Again, this wizard ends up in the front line, but worse: he probably doesn't have the armor to back that up. When his allies are backing him up, however, he's got some serious possibilities to lay the smack down with a sword.
So, again: Four choices, two good, two not so good, and all very very different. Of course, there are eight more possible mixes (the power swap with non-cross-class paragon paths) that could be done, but I won't wax verbose about those.
So, I assert this: Pure multiclassing really does provide a character that's dual-classed, with the emphasis resting on one side or the other. With the number of feats flying around, four isn't too bad a price to pay for this. However, going the paragon path route can produce some much more interesting flavorful options, if you choose the right paragon path. And even some "wrong" paragon paths are still pretty darned interesting (that Wizard/Combat Veteran still sounds awesome to me, flavor-wise. And the Warlord/Wizard of the Spiral Tower is great mechanically, and looks very fun to play.)
As the number of paragon paths and such increases, the set of options will increase as well. But now that I've really surveyed the options for ONE such pairing of classes (admittedly, one that has a lot of synergy), I think there are plenty of fruitful opportunities in multiclassing already available.
EDIT: And yes, there are a few multiclass feats that need to be fixed so that you gain useful access to paragon paths and the like.
