I was very fortunate. My first experience with Champions was back in 1983 when I had the good fortune to play with a group of absolutely stellar gamers from Flying Buffalo Games in Tempe, AZ. They were, for the most part, adults who had graduated from the hack and slash D&D mentality and on to the more mature heroics of Champions (to say nothing of their devotion to genre authenticity). The GMs there were so good at running Champions, that one learned the game's "best practices" simply by osmosis (it should also be noted that 2nd ed Champions had the advantage of being unencumbered by the hundreds of pages of "options" the system has today). It was that experience that I brought with me when I started my own campaigns several years later in another town.
By and large, I never try to drag casual players into a Champions/Hero System game. The system does not really reward those not willing to dig into it and learn it seriously. There are umpteen other RPGs for casual gamers; this system doesn't need to be one of them, IMO. This definitely limits opportunities to play the game, but it also minimizes frustration and maintains one's sanity as well. I can usually tell straight off the bat whether or not a prospective player is right for the group: if they are intimidated by the basic mathmatics required to build a character, then they aren't likely to be a good fit. If the concept of "active cost" is not intuitive (once explained), then they should probably go back to D&D/Pathfinder where the moving parts of the game engine are rarely so exposed. But if they see the elegant interplay between Advantages and Limitations, and grasp the notion that one raises active cost, while the other lowers real cost, then I know I'm dealing someone who won't be stymied with every other rule/mechanic in the game.
As for the unhittable Kobold, one must be prepared to exploit the myriad other ways to hit and hinder a target: AoE (dust thrown in the face could be ruled an ad-hoc AoE Flash attack if necessary), multiple attackers, attacks that target the mind, Presence Attacks, etc. You gotta get creative. And if necessary, put tighter limits on base DCV and combat skill levels. As for reasonable campaign limits, I'm pretty sure every version of the core rules and every genre book I've ever read has sections devoted to the subject.