Well it matches up with the time casters get their more powerful spells and have spare slots for low lewel utility magic. Defy Death aka "1-UP" is late expert when caster get 5th level spells. Indominable is mid paragon when casters get their 1 6th slot and 1 7th slot. And they stack into something fierce.
Frankly it's the fighter's toughness that makes them more of a threat than their attack. It's like the 3e Monk Done Right.
Lets just clarify some things. I'm looking at the last packet (of the play test, not the late release stuff from the cons) and what I'm seeing is:
They have to make a DC 15 Constitution save lets be generous and give them a 16 Constitution score for a bonus of +3. That's a 45% chance of succeeding on the first roll. To succeed on two rolls in a row its a 20.25% chance. For three its 9.1125%. At best the fighter might survive one to two hits and remember these hits can come along at any given time even on the same round.
Fighter drops to 0 makes a save, gets hit again, makes a save, gets hit again fails the save, and goes down all in one round before the healer or the Fighter have a chance to act.
Now lets look at the Wizards spell list at level 8:
Blight - 8d8 necrotic damage half on a save. That's enough with a lucky roll to take out an injured fighter (Average hp for a fighter with +3 con bonus is 68, max damage for the spell is 64). It can certainly take out just about anything that they would be facing at that level.
Evard's Black Tentacles - Area is difficult terrain, Dex save or become restrained and take 3d6 damage. Then take 3d6 damage every round with no save for the duration or until you break free with a Strength check against the spells DC, which is going to be around 15. Which means a 50/50 chance for a Fighter, but other classes and monsters will be in there a while. A fighter can take 3d6 to 9d6 on average before they get out.
Polymorph - Change a target into any beast in the bestiary if they fail a wisdom save (not many creatures or the Fighter has a high wisdom bonus). The target gets the attacks of its new form (which means the Fighter turned into a squirrel get a +1 bonus to attack and -4 for strength mod and deals 1 damage or whatever and must provoke opportunity attacks to get in range to attack[no its not statted out in the bestiary, but I'm sure something like that will be]). Alternatively the Wizard can turn its familiar into a truly fearsome beast to fight off the Fighter while they stand back and cantrip them to death.
Wall of Fire - Encircle a target (with them just inside the wall for the dex save) so they have to take a minimum of 10d8 damage (5d8 with no save) to get out of it.
Now they can cast these spells for half the combats of the day so lets look at their next lower level of spells:
Blink - Half the time when its not your turn you can't be targeted or affected. Very useful if you have a lower level concentration spell going. Oh 0.25% chance of being completely untouchable for 2d6 hours.
Slow - Choose 4 targets, half speed, -2 AC and Dex saves, drops down to one action per round, move or act, but not both. Instant Fighter -> Orc spell.
Stinking Cloud - make a Con save or lose your actions this round.
Wow, what a nice trade off for maybe surviving another round or two (if your really really lucky) as a Fighter. I'm sorry but if a Wizard unloaded on a Fighter at that level the Fighter would go down just from statistical probability alone. Setting the PvP issue aside (because that's generally not how the game is played), most enemies the group will encounter will be devastated too from these things.
Remember the last packet still assumes 4 encounters as an adventuring day so the Wizard can can cast two 4th level spells, three 3rd level spells, three 2nd level spells, and four 1st level spells. Which means if they used half their spells for utility they still had around 1 to 2 spells per encounter. So Blink and Flaming Sphere or any number of combos could be used. While the Fighter is still flailing around trying to kill enemies one at a time (or two at a time if they are lucky with their second attack).
I'm sorry, but the casters still come out miles ahead.