You're the stupid one that put MR blues on an AP jungle champ. I don't think your opinion on what can he do be valid.
What's wrong with MR blues for a tanky char who gains no MR with levels? I can see the logic of mana or AP blues, but I don't see MR being "stupid"...?
Because most people who jungle get MR runes because MR runes or CDR runes are the only blue runes that would really benefit the champ much that are "main" runes or whatever you call it where other kind of runes would be less effective (like putting attack speed runes for blues).
Since most junglers are AD, thats why its common to see MR runes on them. Singed is not AD and no reason for him to get MR over AP since Ap are base blue runes and no fear of magic damage while jungling. Plus faster jungling means more gold and xp to be resistant to AP damage. Also most of singed damage comes from his Q.
MR runes give no efficiency, to his jungling.
Should be pretty obvious, but I was nice enough to spell it out for you.