The only magic items u get from quest drops are failed sets. 40% of failed sets 1) is a pretty bad luck or 2) u're exaggerating or 3) u're doing it wrong and Andy/Meph is not glitched at all (they're not glitched if they drop gold, white items, scrolls, potions, arrows etc).
I have a simple question for u - how many glitched Meph runs u actually did? U may need hundreds to get some decent rares (unless u're extremely lucky). Patience is ur friend.
Meph is easy to find and kill and there're only few gosu rares in game he can't drop in hell (like those +2 amus and grim shields, 200%ed martels and execs etc) - so yes, i think it's worth of farming him. Especially if u can't do cs (yet).