It is a good question which endgame Pokemon deserve a spot in Mid (no higher I'd argue) because of the availability issues. I'd argue that Lapras, Starmie, Gliscor and Sawk are good for Mid. Not so sure about Clefable - no good STAB, slow, needs several turns to set up. Your risk of your set-up ending in a stray crit is very high. Whereas Gliscor and Sawk do not require much set up at all, and Starmie/Lapras help out with dragons and the 8th gym.