Reemove moc in 1vs1 if you remove vanish... People complain about vanish but moc drain is really the worst cheese ever in solo.
Also, no caster are not weak in solo. If you have two CC, you can beat any stealther, you just have to spec correctly with concentration as a RA.
It's just that most solo caster don't know how to play / spec their toon.
I've seen solo wizards/theu/sorc destroy assassins. Let's not speak about BD, SM and now chanters.
This is the ever same excuse for keeping vanish, so 75%+ of SOLO assassins can use it in clean 1v1s, where the caster does not moc.
(even vs moccing lifetap casters i easily hold a 80-90% winrate on my ns)
Vanish is the biggest reason, even before smallmen and 8men rolling over visi solos, for the non-existence of solo casters on Phoenix. If it does not go, solo casters will not return and the rock/paper/scissors balance will remain broken.