I have picked up Diana recently and have a rune page, but I'm not sure if it is any good. I generally win my games, but I feel like I am getting carried through 1-2 fights per game. Anyway, here are my runes:

9x Greater Mark of Insight (0.95 Mpen)
9x Greater Seal of Replenishment (0.41 mana/5)
9x Greater Glyph of Focus (0.65 CDR)
3x Greater Quintessence of Potency (4.95 AP)

The reason I chose these runes is due to Diana's relatively bad early game. This rune setup normally allows me to get 1-2 extra Qs off, and prevents me from going oom before I get Lich Bane (Which is quite a ways into my build)

Side Note: What are peoples thoughts on Blackfire Torch? I have used it in a lot of my games, and have not used it in some of my games. I can't decide if it's worth it.

I read that if you hit with a direct dmg spell and then an AoE spell it will refresh the debuff with the 5%. I was wondering if this is also true the other way around (2.5% hit with direct dmg, and then it refreshes 2.5% instead of 5%) since you will almost always be hitting with Q before you do anything else.

Any help is appreciated, thanks.

I play jungle Diana. Why? Her clear time is absolutely crazy. one Q, and a Shield + Auto Attack will clear a camp (this takes about 1.5 seconds) With a Jungler, you are able to maintain altar control, be higher leveled than anybody else, and win the game. Summoner Spells I bring are Surge and Exhaust.
lolol Surge right? no. It gives you an insane attack speed buff, as well as ability power. Surge was made for Diana, who every three auto attacks basicly gets a free Q. It's insane.
For Masteries I run 0/21/9, taking Movement speed whenever I can.
Shadow Isles' Meta is Bruisers. People who can deal out insane damage while taking some.
Diana is perfect for this, able to leap, A REFRESHABLE SHIELD THAT DOES DAMAGE, a pull back, and a huuuge damaging AoE.
I start Boots + Cloth, 3 red pots and 2 blue. Start at the lower wolve camp and work your way around ganking whenever needed. (Bot, most likely as it's a 2v1 lane.) Maintain heavy altar control and GG.
You want to go for a tank-everything while damaging build. Merc Treads, Rod of Ages, Abyssal Septer, Then Rylais, Deathcap, and Randuins (Active wrecks them) is pretty standard for me, but feel free to throw in a Nashor's Tooth.
9x Greater Mark of Alacrity (15% Attack Speed + Her Passive OP)
9x Flat Armour Yellows.
9x Flat Magic Resist.
3x Movement Quints.

Sorry, way more then you needed, but have fun everythingstomping<3