Well first In shadowbane which was stated above had a mage assassin in its game and was IMO op single target nuker but had no aoe. And for a second example of caster assassins was DnD the original role playing game, i think it was 3.0 when assassins got spells even if you were melee based.
Just pointing those out to everyone saying assassins wont have spells.
Now my actual point is i dont want to see a mage assassin like in shadowbane at all i loved mine but he was too powerful. I also agree with Giz and think stealth needs to be tied to closer range combat as far at mmo goes everyone stealth with range has been too hard to counter and ends up being op or gimp and nothing in between. I think a mid range combat stealth might work though as long as stealth is used as a tool not increase in damage for an opening attack maybe add some cc and have the range dmg not big on damage.
Also i do think the base class should not have spells but one of the promo classes should someone who uses spells as deception not damage. Think maybe clones like DnD or naruto. and other confusion based spells.