I agree that the warzard would work better than the wizlock. Several of the classes just don't work all that well as multiclass options in the current system as it stands. You're blocked by:
* Not getting class abilities which are requirements for paragon paths.
* In some cases, weapon and implement requirements, and / or the language of powers and abilities saying this implement is only for this type of spells, or 'you gain a bonus to your wizard spells with' X, etc.
* Powers that improve based on a mark or a curse, when you don't have that mark or curse as a multiclass.
Of the multiclassing options I've considered for various characters, warlord, paladin, fighter, cleric, and wizard seem to work well and are generally good choices. The other three are situational and use-impaired.
Cleric: Good. Get healing ability. Get Religion. (Could open the door for becoming a ritualist with one feat.) Paragon paths that don't restrict multiclassers (prerequisite is only "cleric class")
Fighter: Good. Skill list is fairly generic but if you were going to take one of the five anyway, it would be worth it. Paragon paths are generally non-restrictive. +1 to attack once per encounter, and target is marked until end of your next turn is so-so.
Paladin: Generally as good as or better than fighter or cleric, but one ability in both Hospitaler and Champion of Order depends on a feature you either can't get, or can only use for one turn per encounter.
Ranger: Great skill choices. Hunter's Quarry doesn't seem to have a time limit like the marks of Fighter and Paladin multiclass choices in the RAW. It only says you get to use Hunter's Quarry once/encounter. A little vague. However, you can't take ANY of the Ranger's paragon paths, as the require the fighting style special feature. So it's only good if you were sticking with your primary class' paragon paths.
Rogue: Highly situational, mostly due to weapon choices. Could be good, could be horrible. You have to compromise on weapons. One specific skill, but a very useful one. Sneak attack does not make it a good choice for most multiclassers because sneak attack is weapon restricted ("I know how to stab someone in the kidneys while they're distracted, but only with a light blade, crossbow, or sling(?!)"). Cat burglar powers are weapon restricted. Daggermaster, obviously, weapon restricted. Master Infiltrator weapon restricted. Shadow Assassin weapon restricted, features an ability that depends on something multiclassers only get once per encounter.
Warlock: Horrible. One skill from warlock's list, which isn't too bad of a list, admittedly. The other part is that you get an at-will power as an encounter power and are considered part of that power's pact. Problems: the RAW seems to nix the idea of combining implements. While the feat lets you use a pact blade or rod, it won't work with your wizard spells. Your staff or orb won't work with your warlock spells. The damage for the at-will you're getting isn't that much better (if at all) than other standard powers for any given class, you'd be getting them for the secondary effect. They kindly say that you can take the warlock paragon paths, golly gee thanks, but:
Doomsayer lets you deal the extra damage of your Warlock's Curse. The one you don't have. Feytouched has abilities that key off of the Fey Pact's teleport. The one you also don't have. Lifestealer's key level 11 ability keys off of Warlock's Curse. Again, you're screwed.
Warlord: Good. See cleric.
Wizard: Good, as many characters don't have the arcana skill on their list and that puts you one feat away from ritual caster. An extra attack, which you can use to get an AoE or a pushing blast your primary class probably doesn't have. Battle Mage should be good for anyone. Blood Mage has some issues with specifying wizard encounter powers on the features list, but you can get one with one feat at 4th level. Spellstorm Mage is nice, and in the RAW for Storm Spell it says "spell" rather than "wizard power" so a warlock should find that useful. Wizard of the Spiral Tower is also good for warlocks because you can use a longsword in place of a wand as an "arcane implement" (again, it doesn't specify whether its for wizard spells or powers, so it's longswords as an implement for any arcane class.)
Initiate of the Faith, Student of the Sword, Soldier of the Faith, Student of Battle, and Arcane Initiate are really pretty good, even if you just take the feat by itself, or just take the feat and a paragon path from the other class.
Warrior of the Wild, Sneak of Shadows, and Pact Initiate are somewhat broken because of prerequisites, unappealing weapon requirements and the language used in paragon path or their dependence on abilities multiclassers can't get, or due to the impaired use of the ability the feat gives you. The RAW for those classes and the way the feats were set up just limits the attractiveness of these three. They should have been more careful with the writing on those three classes, as they made a lot of things too specific to be useful to anyone else.