I don't care about teirs or smogon so I want to make some broken as fuck guys to play my freinds who like to use legendaries

Is evasion really this unbeatable thing, Sandslash has been a favorite since Gen 1 so I was thinking of taking him with sandveil, sand attack, and sandstorm with dig and Rockslide to round him out. Set him up, sand storm spam sand attack

What IVs should I train him with, his speed and special defense isn't that good so would a Attack/Defense be good enough to take him up the battle tower? (as a stand alone, not a part of a team)

and should I give him quick claw or smooth rock?