most of time there will be anyway enough champions with damage and burst, top laners nowdays are only bruisers, mid laners are mages or assasins, etc. What i mean is that you don't really want a support to be focused only on damage, but how I said, you can just rush ardent and opt for AP items insead of support if you really want. But just to understand, keeping your team alive and buffing them (indirectly with ardent and if you really want another slot for zeke) they will be able to cover the damage you would do in full ap/on-hit state, and as a bonus, they will remain alive (if they're not monkeys).

While most of kayle guides probably are focused only on her scaling and late game damage I try to make max usage of her kit from very early stepts of game with that strategy, now if you want that or you prefer an bursting one is up to you, I not claim that is the perfect or correct way to play kayle, but for support role I think is the optimal one.

Also regarding her W, the mana cost increase with it's rank, so maxing W mean you also need more mana/mana regen to keep it up and not waste, Kayle it's extremly mana hungry early game.

amm same..