Hmm. This is very interesting.
I'm not exactly sure what you mean by "human," though, since Hylians and humans are extremely close together and the games basically mix them up as one. :\ Plus, you've named a bunch of non-human female characters to back up your claim...? You do realize that you're limiting your question so much that it's just as hard to name five very important female characters...?
Let's see...
(*spoilers ahead*)
1.)
Shad from Twilight Princess. You could not get to the City in the Sky without him!
2.)
Auru from Twilight Princess as well. He helped you get to the Gerudo Desert and also appeared in Hyrule Castle to save you near the end.
3.)
Rusl from Twilight Princess, again. XD He was an important beginning character and was later revealed to be part of the Resistance later on in the game. He helps you get to the Sacred Grove.
4.) I'm not completely sure about this one, but I guess
Byrne from Spirit Tracks. He saves your life at the end as well. ;D
5.)
Master Eddo from Phantom Hourglass. He gives you the Cannon and later the Salvage Arm. Can't do without those! ^_^
Since I wasn't so sure about Byrne, I'll give you #6:
6.)
Rauru from Ocarina of Time. As the Sage of Light, he tells Adult Link about his destiny and starts him on his quest seven years into the future.
You know what? I could keep on going on.
7.) The
Happy Mask Salesman from Ocarina of Time and Majora's Mask. How could we
possibly forget about him? XD I guess it's self-explanatory.
8.)
Tingle from a bunch of games. He draws you maps. In The Wind Waker, it's required for you to bring maps to him to get them deciphered.
9.) The infamous
Old Man! He is found in various caves and gives you helpful items. ;D
10.)
Linebeck from Phantom Hourglass. He is the captain of the ship you ride throughout the entire game. He risks his life for you in the last battle!
11.)
Oshus from Phantom Hourglass as well. He is actually the Ocean King. ^_^
12.)
Beedle from The Wind Waker, Phantom Hourglass, and Spirit Tracks. He sells you a bunch of things. The stuff that he sells is sometimes required to progress through the game.
13.)
Alfonzo from Spirit Tracks. He's Link's mentor and is important to the plot.
14.)
Niko from The Wind Waker and Spirit Tracks. He actually lived through all of that!
He tells you to do things in TWW and then tells you stories in ST. You get the Stamp Book from him.
15.)
Ferrus from Spirit Tracks. He gives you a map showing how to get to the Snow Temple. He will later appear in various points in the game.
16.)
Barnes from Twilight Princess. He sells you Bombs, which are needed to get through the game.
17.) Although deceased, the
Hero's Shade from Twilight Princess could count since you could say that he was once human during his lifetime. :\ The Hero's Shade teaches you seven moves which all greatly help you during your quest.
18.)
Colin from Twilight Princess. He gives you the Fishing Rod, which is required. He also plays a big role in the game.
19.)
Mayor Bo from Twilight Princess gives you the Iron Boots and also teaches you how to sumo wrestle. ;D
20.)
Coro from Twilight Princess gives you the Lantern, which is required. He will also give you an extra Bottle!
21.)
Renado, the shaman of Kakariko Village in Twilight Princess. He is helpful in so many ways, the most important being the recovery of Ilia's memory.
22.)
Talo from Twilight Princess. He was one of the children that was kidnapped in the beginning of the game. He also forces you to teach him sword moves, and then is later found overlooking Kakariko Village to make sure there's no danger.
23.)
Ingo from Ocarina of Time. He races you and then gives you Epona.
24.)
Guru-Guru from Ocarina of Time. He teaches you the Song of Storms.
25.) The
King of Red Lions, A.K.A.
King Daphnes Nohansen Hyrule is, of course, very important to The Wind Waker's storyline.
I realized that there's a lot of important male characters, but you did mention that you can't just meet them once or twice in the game, so I had to leave them out! >_<
