Flaming Skin is a source skill so you're not likely to use it excessively often. It also only lasts two turns. Certainly it's not a bad skill by any means but I wouldn't design my combat strategies around it.
That being said, I Really like the idea of someone with Necro tossing both Death Wish and Living on the Edge onto a character with Pyromancy, and them standing in the middle of their flames nuking everything down with Elemental Affinity. They can't die, but they can sit there at 1 health and deal double damage!
I also like combining Hydrosophist with Summons. Most of the Hydrosophist healing abilities aren't int based so such a "mage" can completely ignore Int, focus on wits and memory, and give your team a first strike and endless distractions for the opponent.