I think the 5e Wiz is a solid (i.e. average or middle-tier) class at low-mid levels.
I'm curious to see your ranking of the classes at low levels. I'd put the wizard high on that list at low levels, and it only gets higher. Between very good out of combat utility AND high combat effectiveness, I can't see it being "mid tier."
What remains to be seen, what I fear, is that the poverty of high -level slots was 'a nerf too far' (late in the playtest). One single 7th level spell that can fizzle when the Fighter is attacking 6 times per round multiple times per day,
If the fighter is attacking six times, he's using action surge. That's a once (twice at very high level) between rests ability. The wizard gets arcane recovery, so he can recover spells when the fighter is recovering action surge (granted, if the DM often allows for multiple short rests, the fighter gets a bigger benefit here).
As for 7th level spells fizzling, I don't have my PHB with me, but looking at the basic rules, none of the spells are particularly fizzle prone.
Delayed Blast fireball: good damage (12-13d6) to many targets, great against mobs of opponents which are very dangerous with bounded accuracy.
Finger of Death: amazing damage on a failed save, ok damage on a successful save (you're looking at around 25 points of damage even if the save is successful).
Mordenkainen's sword: weak for a 7th level spell, but it doesn't "fizzle" unless the mage fails a concentration check.
Teleport: old standby, useful as ever.
Plenty to go by here, but if the wizard wants, he can scale up his lower level spells instead (heck, fireball as a 7th level spell is nearly the same as delayed blast fireball, just a tad less situational utility)
Idunno. Have not playtested high -level, hope to be proven wrong.
Yes, we'll have to see, but I'll be surprised if the mage comes off as anything but extremely strong at high levels.