Conjuring problematic situations is an important part of theory-crafting. The worst problems people have been able to conjure rely on 1) Getting what you need from the two possible creatures this card creates at the exact right time, 2) This perm not getting destroyed, and 3) You not getting rushed before it has any effect at all.
Out of these three conditions, the third is the least likely to occur. Why? That one turn you need to wait before you can actually summon the creature.
If it gets destroyed, which it most often will if your opponent expects you to play any perms at all, you have to draw another, which can often take several turns.
If you don't get Rays when you need them but keep getting Blights, your Hope won't be be played for many, many turns.
This is not a very practical card, and the theoretic problems people conjure don't consider actual practicality, similarly to how someone inexperienced with actual gameplay might complain about the
potential overpoweredness of Mutation.
In the current metagame, this has almost no place, as speed dominates. Similarly, Mutation has little place because it's unreliable and usually costs you card advantage. Doesn't really matter if you sometimes get a kickass mutant/get the creature you need with this perm, because that Lava rush will still have done more damage than you/rushed you to death, even during those lucky moments. And that's not even considering the dozens of things that can screw both cards and combos up completely.
I wouldn't use this in a RoL/Hope deck at all because of the slowness, PC vulnerability and waste of a card space. It's a redundant card in that setup because Fractal gives you everything you need and more, and you will want six copies of Rays either way.
I wouldn't use it in a Blight OTK deck either, for the same reasons and two additional ones: it would cost me
I need to hit with the combo ASAP, since it's a pretty vulnerable strategy. Since I need speed even more than in RoL/Hope, the cost of this perm pretty much ruins it. Secondly, I would need to squeeze in
to be able to use it. Making a vulnerable combo deck more unstable? No thanks.
Where would I use it? I would use it with Druids for sure (sweet! finally an endless supply of Mutation targets that isn't really expensive!), I would use it with Bone Wall and possibly Unstable Gas, and I would make all sorts of semi-good rainbow decks with it. Can this perm be powerful? Yes, if used right, which is difficult. Can it be overpowered even in the luckiest of scenarios? Not even close.