What's your first impression of Eureka?

[Fynlar]

the achievement of solo floor 200 is achievable by only 1 job with a hefty amount of RNG, moreover the rewards are apparebtly needed for some of the fashion report conditions and let's not forget that before the sustain potion it was not possible for dps to go beyond floor 130 and for healers about floor 160

That's what Reyhart was probably talking about (minus the fashion report thing) while potd has been promoted as solo achievable even in the lower floors it really wasn't

Besides I remember a lengthy forum post saying that the solo 1-200 floor achievement was BS because of the sheer luck you need to reach it

Again, it's not really necessary to go all the way to 200 to be able to get good stuff out of it.

The second part of that question is how long it takes for someone to clear PotD solo compared to a team. Because, in the end gaining Xp in Eureka on your own is doable, it just takes much much more time.

Progress in POTD solo doesn't take THAT much of a hit. I was still getting lots of bank off my solo runs. Progress in Eureka solo (and by that, I truly mean solo, in other words no mooching off of a FATE train) is utterly abysmal in comparison. They're so many realms apart that there's really no comparison.