Sleek wands, each mage has his own set of sleek wands with aura, barrier, shield spells. Somewhere in the world. Search on Dios and here for more info.

For assassin - dont remember exactly, I played them loong ago. I just think that you should not gear for damroll only, keep in mind hitroll and HPs as well. 25 should be enough, I think, but not sure. I am mage player, not warrior-classes

Some classes (including assassin) have easy ways to escape. This is blind. So, if he summoned you, dirt/dust him first. Then you can vanish and run safely (unless he has cure blindness preps, which are not so easy to get and if he has them...well, at least you die to a veteran )

Practice all your weapon skills. Hone and love all your defense skills. Read about them on Dios. AP should not outmelee you, generally assassins are better in melee, imo, especially if AP uses spear, not axe.

The problem of assassin is bash/trip. So, if you see enemy around (where command) or going to hunt, use enlarging preps. They are easy to get. Then they will be surprised by missing bashes.

AP does not need hitroll as you do. As I know, the chance to make kote/kan is dependant from your hitroll. Thats why you need it.