It's Solas' self-flagellation that makes him come across so negatively on occasion in my eyes. He's full of himself, but sometimes he can be so hard on himself too.
That's the thing that confuses me about Cole. The Nightmare is what Compassion can become as the Divine said, but Cole's fear is Despair. Is it because he was once represented Mercy more than Compassion with all those mercy killings?
Well, let's face it - what seems to motivate him more to do what he thinks needs to be done is his overwhelming sense of guilt, rather than pride itself.
As for Cole - I don't really think it's that confusing, if what I think they're doing is correct.
Like in our world, the concepts and emotions (like Compassion, Love, Desire, Pride, etc) AREN'T just one, fixed thing that can be easily categorized - even if we try, just for the sake of quick identification. They can mean many things or can be pulled in different directions. Same with spirits IMO - the emotions or concepts they embody lie on a complex spectrum scale. It's not just Compassion - Despair or Wisdom - Pride. There are other directions they can be pulled, especially if they gain enough nuance, or intersect or resonate with other concepts.
I think instead of visualizing the whole thing as separate, linear graphs, we should think about it sort of like emotion wheel.
... or perhaps even something more complicated than that, with some things being closer to others, but never really separate. It's all inter-connected 
IMO, the spirits (like, regular, simple spirits) sort of embody the purest idea or a concept - in that sense they're pure and light, but also fragile. They don't have enough complexity/personality to grasp things beyond their narrow concept of the idea they like to stick to, which is why they can also be easily twisted.
The more they develop personality and understanding, the stronger they become, and while it helps to understand things more, it also 'muddles' the original concept - it expands and resonates with other things. The more they understand the world, the more things become complex, but also muddled, until the initial concept they've stuck to becomes more of a driving force or strongest personality trait, rather than a thing that defines everything they do. At one point or another a simple spirit likely becomes so complex, that they likely cross the vague boundary between a regular spirit and a person.
It's likely important that a person shouldn't forget what lies at their core, so they could retain what makes them THEM, and not become twisted, but they have other things that define them as well.
This is likely why Solas may be defined by both his need to gather and share knowledge, or think that only he can do something to save the elves, but it's no less important for him to be compassionate or motivated by his sense of justice.
In the same way Nightmare may be a being that has never crossed to our world, but it became so complex in itself, that Despair or anything else is too simple of a concept to describe it in its whole. It's more than that, yet at its core there likely lies a very twisted and mostly forgotten understanding of Compassion.