This is just my 2 cents worth concerning the "balance" of magicka-based classes. Take what you will from it. I have a character in every class that I run anywhere from solo, to small man, to large groups in Cyrodiil. I try to be a "purist" when it comes to magicka-builds (ie: I try to run as many class-based skills as possible... but there's usually one or two non-class skills in the bulids). As a little insight to how I make my builds: I normally stack armor sets toward the highest 100% uptime damage possible and then tailor my regen/resistances around those builds. I always shoot for a 5l/1m/1h setup with at least 2k crit resist, 10k penetration, 23k resistances, and 1700 regen. This is how I would rate the "effectiveness" of each class:

#1. MagSorc (Innate, Netch, Mighty Chudan) High burst and mobility. They're the "executioner" of group play. I will get the killing blow. I don't play with pets, though- so my self heals are lacking.

#2. MagBlade (Innate, War Maiden, Slimecraw) High damage and high group heals. It feels amazing to Lotus Fan into a group, burst with Soul Siphon, and then Sap away- all while adding heals to my party. The only thing I miss is the speed now that it's been taken away from Double Take.

#3. MagDK (Innate, Silks, Domihaus) Good damage with a lot of group utility. Though their heals are selfish- my DK adds snares, immobilizers, and fantastic synergizes to my party. I wish they had a better shield or small self purge.

#4. MagPlar (Soulshine, War Maiden, Mighty Chudan) Very good group heals/utility and good damage. My channeled abilities (Dark Flare, jabs, jesus beam, and soul assault hit like a mother). I wish that we had a functioning immobilizer and Dark Flare's cast time was moved to .5 seconds.

#5. MagNecro (Innate, Rattlecage, Valkyn Skoria) I absolutely love the synergies and group utility for these guys. My only complaint is that they're a little too "giving" and they don't really have some pretty major self-buffs. Some form of major/minor expedition added to one of their skills would be appreciated and their immobilizer should do a little damage.

#6. MagDen (Innate, Ysgramor, Domihaus) As you know- they've got a ton of immobilizers and stuns that annoy people. Their damage is lacking (but there's been a few builds lately that have shown potential). The only thing I'd like to see is that they get the old Arctic Blast back and perhaps make Feral Guardian viable in PVP.

Again- I'm sure everyone has their opinions of the "meta" for each class- but I'm sure some of you who play multiple classes can agree on some of my points.