The main problem of wiz3 is that all ele and warlock skills have rather long cd. It means that Pyro can fill this downtime with flamegrounds and fireballs (but not in a party). Fire pillar does good damage and locks mobs in place so the tank can lure them to the fp and step away.
I really don’t know what choice is better though.
Speaking about skils falling off at higher levels, it happens to ele skills too. You can search that video where a quick cast meteor barely damages a mob at 200+.
I played a non quick cast ele2 in icbt2 and had no problem with casting any of its spells without surespell and quck cast. Just choose the right moment for it.
I also played both pyro2 and wiz3 in ktos. I can say that wiz 3 was a real pain for me even in tenet. Magic missile is so much weaker than flameground, and you basically press it twice every 15 seconds and wait bc energy bolt is so weak that mobs will overwhelm you. It may depend on your personal playstyle though, many ppl enjoy magic missile.
To me, pyro2 felt like 10x faster and enjoyable in tenet and later on.
About that rating of characters for Earth tower - we need more feedback and videos from other parties, not just 1 or 2, to judge what is better. I can hardly belive that ele is better than overpowered archers there, but time will tell.