I don't see why you wouldn't take Kayle as support. She heals better than most supports. And has an additional shield on top of that. What am I missing that makes her not support like?

well i understand kayle might be versatile..just I have limited IP :P im already used to useing other champs for other roles. I was using soraka as supprot but didnt like her fairly weak harrass vs some opps...then i tried lux and liked it, but didnt like the weak sustain...so kayle seems like a good middle ground.
Obviously im not a stupid support i dont attack minions i try to give all income to adc

Kayle can support, sure, but I hate supporting as her. Hybrid AS is definitely the most fun way to go, if you ask me. Berserker's Greaves for initial AS, then Nashor's Tooth for CDR and mana regen. Nashor's also gives you AP and AS.

Next you can get Malady, The Black Cleaver, Guinsoo's Rageblade, Madred's Bloodrazor, etc.

Your choices after Nashor's should be according to the composition of the enemy team and whether they're stacking armor or magic resist.

Personally, I turn support Kayle into a double AD lane, giving all the farm the the "main carry" while harassing the enemies with my E. Kayle's damage needs a nerf because I can sit back and E all day long and just shred HP lvls 1-5 quite easily. Lvl 6 I can make myself or my ally invulnerable. It's one of the most effective kill lanes I've ever done.

So I tried it today, not a bad heal. However, the lack of hard CC is where kayle falls short. The ult is great though. If she had a stun I would recommend it or even a stronger slow. The problem is after the lane phase, kayle doesn't provide the same utility as Taric, Sona, Raka ect. with auras. I play around the bottom of gold in ranked btw.