On Min-Maxing, and mechanics

[Chalcoco]

I'm very familiar with Din's curse, but decisions there are pretty straightforward. Between the upper limits on skill count, the mutation system, and a few of the skills that are new to me, with entirely new mechanics (passive auras, and sustained skills) there's a lot more depth here that leaves me with questions on making a character most effective.

I haven't hit a wall yet, but after a couple more characters I would like to make a couple of themed characters that make the most out of the new mechanics, so I have some questions.

1. I have yet to land one, but I dug through the files and saw that the few unique skills are really just existing skills with modifiers built in. So, are they advantageous in that:
   
   • Three skill slots for the price of one?
   • They can also get two additional modifiers so they can actually total up to 4?
   • All of the above
   • I'm missing something completely.
2. What's the best balance on skill selection? For Din's Curse, obviously when making hybrid classes one good strategy was to get classes with not just skill synergy but basic synergies as well. Here, you can get A LOT of basic skills, so what ends up being a good balance? It's VERY tempting to just load up on basic skills focusing on a few specific attributes.
   
   • Firstly, it seems this makes some skills much less effective, ie. if you get the dexterity defense bonuses, and you're already investing in dexterity, things like dodge, block, and parry are much less effective.
     
     I know some "counter-attack" skills require specific defense reactions. So, they offer value on that side, but two skill points to add 15 defense vs a single point to add 200+ defense seems to indicate to me I should be pushing for basic skills, if I want to maximize my defense and don't need specific reactions for things like Riposite. (It also means bonuses from Shield Mastery should be awesome)
     
     Likewise, some of the mana basics vs skills like concentration & zen. (so it effectively becomes whether you want to invest via attribute points or skill points) I'm kinda just wondering if this is a matter of making choices with limited character resources.
     
   • Secondly, it seems skills like Dexterity to some degree, but especially skills like Unholy Vitality are very powerful. Getting spirit +mana passives and investing attribute points into spirit, and skill points into Unholy Vitality means you can get the best of both worlds. (And can invest in vitality & strength bonuses to further maximize it). [Note: Very excited to try this on my next character]
3. What exactly is Zombie Resistance? Does it function somewhat like the race based mutations? It's granted by Earth Link, but it's not on any of the character stat menus that I could see. It isn't prevalent so it seems I can effectively ignore it, but I am curious.
   
4. Finally, NPC partners? Worth investing in? I typically just grab one on a new character, and once the inevitably succumb to the rigors of adventuring, grab another just before I advance the difficulty and repeat the process.
   Can they have all abilities in the game? Seems they just have those from specific archetypes, and I've only seen a sub-set of "enchancements" (mutations) on them, but they have very varied.
   So I was curious just how different they can be.

TLDR; Seems with some skills that add secondary attributes, vs basic skills, it's really a matter of resource management? How to maximize?
Unique skills are about skill slot optimization?