I'd add two models. Born Free RV, I would add to either tier 1 or 2 because of the molded fiberglass. I would also add the Winnebago View to tier 2. Both have completely seamless construction in the front
I'd probably add two tiers to Jeffcarp's list. I would add the FR Sunseeker, Solera, and Forester to a tier between 3 and 4. They are not as good with fit/finish as a Coach House, but they do have a fiberglass roof, fiberglass front and rear endcaps (which make a large difference when it comes to leaks, as it protects the corners where the wind comes in. I'd also toss Jayco in as well because their rigs also have fiberglass end caps and a fiberglass roof.
Anything on tier 4 like Coachmen, I would not consider new. Class Cs are pricy, and for bang per buck, Forest River's offerings are the best value going, and it is hard to do better than their offerings at the price point they are at. You do get what you pay for.