not sure, it will lose some sustain cards, and the highroll ones, this 3 cards you are sharing, have potential with all the slots that will be open after Projext OPsday and the mountain giant rotates out. Astromancer Solarian the most, all primes fits perfectly in higlander archtypes.
Edith: the fourth one, is dificult to say, when is a good card for clears, feels a bit weak most of the time.
As long as Zephyrus, Alexstrasza and Reno are viable, a highlander mage will be somewhere in the format. It may not be tier 1, but it will be a solid tier 2 deck barring Demon Hunter absolutely decimating the balance between the existing classes in some unforeseen way.
Highlander Mage needs some defense against face decks to be tier 1, with the rotation of zilly it is gonna be harder for mage... we will see if we got some good defensive cards. But i think the highlander package alone ( Zephy etc..) is good enough to make it tier 2 or 3
1. Yes, it is still going to be viable. It loses Luna's Pocket Galaxy, which is a big deal, but I think you can play without that, since is keeping most offensive and defensive options and all decks are going to be hit.
I think a lot of the cards it uses will still be around. It loses Luna's Pocket Galaxy, but so many times that card just didn't show up in my hand. It's really hard to say what type of spot the deck will be in because other decks are losing things as well so its not a one sided loss.