I put Phage into the Orb of Insight and it produced a big zero, so it looks like Jeska's reincarnation is waiting til at least the next set. Akroma also produced a zero.
As for Arcanis, I think if played under the right circumstances, he could be incredible, but he has the limitation of being a creature, which brings summoning sickness with it. So without any mana acceleration, he's coming out on turn 6 (which is unlikely unless you're playing mono-blue). The draw ability can't be used til turn 7, which is very good, but maybe not very game-altering. His second ability almost counter-acts the first in that if you bounce him, he's coming back with summoning sickness. Arcanis is a big commitment, maybe too big of a commitment for what he delivers. The fact that he's a legend doesn't really help matters.
I expect all of these dudes to be huge in limited, but very difficult to play in constructed.
Out like trout,
Duster