For anyone just starting to read this, new information was being released as I was posting through the next few pages, so the newer posts have better predictions for solid builds and I'd start with those if I were you!
Here is my guess to the speculative top tiered classes, based on what I've seen. (Most of the betas I've played, I've been correct on my predictive endgame theorycrafting.) I really wish I could see some examples of Racial skills, but I'm just writing this for fun.
Wood Elf>Redguard>Argonian -- Nightblade Assassin with Bow and Medium Armor.
Wood Elf/Redguard/Argonian will be the "sneak" type race for their alliances. Pair this with a Bow for Snipe out of the sneak, and Medium armor for maximum mobility (less expensive rolls, and bow gives you giant speed boost out of rolls). Nightblade Assassin for Marked Target and "finishing" ultimate. Guessing this will be a very fun setup if you like 'ranger' type characters.
MAGIC: EDIT: for fire dps, looks like Dark Elf racials are the biznz.
High Elf>Dark Elf>Breton -- Ardent Flame DK with a Fire type Destruction staff and light armor.
Those being the magic focused races of their alliances. Pair them with a Destruction staff doing Fire damage and Ardent Flame DK's +Fire damage passives for maximum magic DPS. I speculate this will be the highest DPS setup in the game. Typical fire mage, not as much utility (blink and lightning shield) as going lightning destruction staff and lightning mage..and they will probably have higher burst potential as long as their Ultimate is active. Breton would probably be best for a utility lightning mage.
Orc or Nord. Aedric Spear Templar for the +Power and the charge. Will synergize nicely with the increase in weapon power on a 2H build (scaling with Momentum, too). The +% damage on abilities scales well with the high damage per hit, on any ability with cooldowns like everything we've seen so far. Having two charges is the buttsex. And, using Heavy Armor will work better as the berserker class. 25% reduction to snare effects in light armor isn't worth it, and nothing else looks that promising either.
Khajiit, Orc, or Nord. Draconic Power DK, heavy armor, sword/board. Look at all that life regen... Maybe even an Argonian would work well for this. Look at all your passive defense/resistances... +12% +3%x5 armor items in heals taken... I've thought about this one more than any other one because I plan on tanking. I think that as far as an actual group goes, this will be the best tanks. As far as soloing as a tank..it depends on how low our damage is. We can always take off the slotted ability that sacrifices 8% damage for resistance/armor and finagle things around a bit, so I think it'll be fine for soloing as well. When I've min/max calculated all the numbers that are on the boards so far, this came out with the highest positive scores of any other class. But, I mean..if they can chug potions, or get their resitances to a closer ratio to these, that number would close rapidly because our damage is a bit shitty...
Khajiit, Orc, or Redguard. Use a dagger for 5% crit and a mace in offhand for armor piercing, other players should have higher armor ratings than avg npc's because of potions/etc, so it should add bonuses more often than 1/2 the time. 1/2 the time would makeit = swords, but it will almost definitely be more than 1/2..and if it's on lower armored players, chances are that your melee weapon will already be hitting like a fuckton hammer anyway. Okay, well anyways, use a dagger in mainhand and a mace in offhand (since you can't use another dagger in offhand.) Moving on, you will probably want to be a Shadow Nightblade for this class because they're the best at chasing (50% move speed for 10 seconds IIRC while chasing someone..as well as a slow.) Since DW doesn't give much chase options, this is almost required.. or a Dark Mage to stun and chase..but anyway, I don't plan on playing Dual Wield EVER so I'll let you figure this out on your own. I'd go Heavy Armor, even though the obvious answer is Medium armor for this class. (I JUST said you'd need to be good at chasing, right?? Well, you need to be even better at melee distance fighting, which heavy armor looks to excell at.)
Healing: Edit: to boost early game, Argonian get +15% XP in resto spells and heals affect them more! Bottaboom!
This one feels pretty obvious, as a Restoring Light Templar for the dispels and AOE protections, rolling with a restoration staff and a shield with light armor.... But, I'm thinking that a Siphoning Nightblade using a restoration staff could be pretty awesome. They wouldn't get as magicka drained.
I'm thinking a Frost Destruction staff on a Siphoning Nightblade will be the very best overall class in the game. Huge utility, passive damage, and self-heals while never running out of mana. I'd plop this shit on a Khajiit and call it a good day to everyone else in cyrodiil, cause you raping everyone in sight. Okay, but seriously, I think this is what I'll end up playing if this works out AT ALL later in Beta. Right now I'm having too much fun playing a tank, because that's what I always play.
I know there's a twenty thousand more options or whatever, and I didn't go into what exact 5 skills I'd couple with my ultimates and why for each "class"..if you can even call them classes...but whatever, I'm horny. Time to go cry and eat myself to sleep.