Basically, the last item I build varies depending on the game i'm playing

if the enemy team has 1 or 2 players who are causing trouble I build another phantom dancer, however, if I'm playing a well balanced team, or one which regularly engages in teamfights, I'll build a nashors.

My friend completely disagrees with me and would build a G.A.

that extra 12 armour is going to help alot early game, but late game it won't be so usefull.. I dont bother with runes that scale as it generally isnt worth it

Kayle can't really do burst damage, but I've 3-hit so many champs before that that isnt really important. For the tougher ones, in a long fight I tend to find that heal is more usefull than ignite.

flash is just flash.. it's good

use kayle's ult on yourself just before you die: this will bait the whole nearby enemy team towards you (they'll generally all want the kill) and with the whole enemy team nearby you can make the most out of that splash damage and pick up a few extra kills
it will also allow ant ignite's, etc to run out before you heal/divine blessing yourself, and allows loads of regeneration through lifesteal while you're invincible, so an escape isn't uncommon at all