viso by itself? no.
Viso for lvl 18:
crown base, eth/rep, 50%+ edef, viso. 2 os and/or life is a big bonus, as is 5% base ar mod.
viso for lvl 30:
grand crown or grim helm base, 80%+ edef, viso, 2 os and/or life is a big bonus, as is 5% base ar mod.
if its not at or VERY NEAR those type stats its charsi. and if it's barb helm for either and big defense then maybe worth something.
but 99/100 or more visos posted are charsi.