Disclaimer
This guide is a compilation of the knowledge of the members of Rohane's Bane and is maintained by stacigh. Please do not reproduce any of the content found in this guide without prior consent of the creator.
How To Use This Guide
During your game pay, choose two skills and work at getting them to level 13. Bring your innate's up to level 11 each.
Once you have achieved that, stop spending your skill points. When you are about to fight King Terask II, equip the final weapons to each character, then (and only then) max out any skills that were not maxxed out with the weapon bonuses.
If you got full equipment for one character (i.e.: you got the final weapon & armour for Talinia) then you can put the skill points in some of the other recommended categories, which are explained below.
Note: Almost every final weapon increases +2 to every skill. Every final armour increases +4 to the innate's
As a rule of thumb, gradually increase the skill points. Why? Well, if you only have critical attack up to 13 but you don't have any other skills, you're really stuck and will have a difficult time defending yourself and the other members of your party.
Rohane
You should start by investing the bulk of your skill points in defense, as you will be fighting enemies solo until you get Mipsy half way through the first chapter.
Recommended Skill Set
Rohane's final weapon is Sword of Apocalypse, it adds on +2 to every skill.
A Note about Father's Sword
Father's Sword is an awesome weapon if your critical attacks and damage increase skills are maxxed. It only works on Terask II but it works in all game modes. There are rumors about how it gives you the worst prize. This is inaccurate. Prizes for NeoQuest II are given out at random. Father's Sword does not guarantee you the best nor the worst prize in the game.
Skill Explanations
Critical Attacks: Increases the chance of a critical hit.
Damage Increase: This will increase the amount of damage you do.
Innate defense: It will increase your resistance to magic.
Innate Haste: This will increase how fast your turn comes. It's very important even though there's Group Haste.
If you have any extra skill points I think Stunning Strikes may be a good place. You don't have to actually spend the points if you don't want to though.
Mipsy
Even with max direct damage she will not hit more than the number of her hit points. 
Recommended Skill Set
Mipsy's final weapon is Wand of Reality, it's the only one that doesn't add +2 to every skill Instead of using this wand, I recommend the Unbending Wand. It gives +4 to Direct Damage, good huh?
Skill Explanations
Direct Damage: It does 100 damage at max, and if I remember correctly, it does 85 damage at level 13. It's resisted a lot against KT2, so some people don't use it. I, however, recommend it.
Group Haste: You have to cast this spell, but it's worth it because it'll make your group's turns come faster.
Innate defense: It will increase your defense. Very important even though there's Group Shielding.
Innate Haste: This will increase how fast your turn comes. It's very important even though there's Group Haste.
If you have any extra skill points for Mipsy, I think you might want to consider investing in Damage Shields. Mipsy's considerably weak next to Rohane, Talinia and Velm. Make sure to keep an eye on her health level as she's usually the first one to die.
Talinia
Okay, so she's a bit of a weakling in the beginning, but she's good; real good. It's possible to play the game without her but, if this is your first time playing or you are on insane for the first time, I don't recommend it.
Recommended Skill Set
A Note on Bow Damage
At 11 points in bow damage you will be able to hit 4 opponents. Some people find that satisfactory while others do not. The numbers 11, 12 & 13 are supported in this guide.
Skill Explanations
Bow Damage: This will increase the amount of damage Talinia will do.
Multiple
Targets: It allows you attack multiple opponents at once, it is better
than Group Direct Damage, which is one of Mipsy's skill because this
will do over 100 sometimes, and Group Direct Damage will do only 64
damage to each opponent.
Innate Magic Resistance: It will increase your resistance to magic.
Innate Haste: This will increase how fast your turn comes, it's very important even though there's Group Haste.
If you have any extra skill points I think range or shockwave would be best.
Talinia's Alternative Skill Set
There is no right or wrong way to do skill sets, so there is of course an alternative for every character. However, Talinia has what I like to call the widest range of skills within all of the characters. That is the reason there is an alternate skill set for Talinia. The alternate skill set is a "stalling" skill set.
Shockwave: 10
Range: 10
Slowing: 6
Innate Magic Resistance: 11
Innate Haste: 11
If you don't find this Alternative to your liking, you can of course, move them around more... I suggest you keep Range one of the highest because it works on King Terask II more often.
*Note: Talinia's slowing will have more effect if Mipsy has slowing. You can also use a slowing potion in addition rather than a spell.
Velm
Velm has joined your party." The five best words in NeoQuest II. It's usually by the time I make it to Chapter 3 that I'm dying for Velm to join my party. Velm is, in my very humble opinion, the best and most valuable character in your party. 
Recommended Skill Set
Velm's quite special because of his healing abilities. Wouldn't it be a shame if your whole group was a little low on health and you only had single healing? And you have to keep track of who needs to heal at what time... It's a hassle, no doubt!
Skill Explanations:
If you have any extra skill points you should put them into memorization.