I find Kayle actually has one of the slowest melee animations at level 1. I mean, it's so front loaded, the wind up to the swing is way too long. I've been next to a creep with an auto attack ready and I right click them to get the last hit, and Tryndamere who's like 2 steps away, right clicks about the same time, he gets the last hit because his swing is almost instant.
But yes, wise usage of righteous fury can get you last hits if you're careful (IE, not just spamming it in any mob of creeps just because it has splash damage).
From Zhonya's or Gunblade, I'll go Zhonya's usually. I like building Kayle hybrid early on, but later on even with her passive I find it better to go pure AP or pure DPS. Pure AP because zhonya's ring doesn't take nicely to anything besides pure AP. With pure AP you get more splash damage (relative to normal damage), and your normal damage approaches about even split between physical and magical (which can be good if they armor stack). With DPS, an Item like Infinity Edge doesn't take nicely to anything besdies more DPS items that have critical chance (or elixirs). I find that if I take DPS even though I have two AP items in my build (nashors+rageblade) I can do as much DPS as pretty most other carries due to her passive while still retaining decently powerful heal and nuke.
Overall I'm just not that big a fan of the gunblade for any champ, even hybrids like Kayle. Spell vamp is about the ****tiest stat you can get in the game (oh, my reckoning hit you for 400 damage, so I'm healed for.... right... 52 health every... 4.8 seconds (with full cooldown reduction)). Lifesteal also really isn't good on ranged carries as the point is that you're not supposed to be taking damage in the first place. Lifesteal is for melee carries who expect to be taking damage while dealing it. Also, if you get stunned, good luck using lifesteal to help you survive (but then again, we wouldn't be getting CC'd since we're the ranged carry, right?). In terms of pure efficiency, 60AD and 75 AP for 3625 in one item slot ain't bad at all (BF Sword+Long sword+Needlessly Large Rod=3865 gold and you get 60 AD and 80 AP), the problem is, late game it's actually better to specialize in either DPS or AP for Kayle due to the nature of items such as Infinity Edge and Zhonya's Ring.
