They mean that the thing that makes those things powerful isn't the martial side, but the casting side. The martial side is just more on top of what was already powerful. RKV on a paladin chassis isn't nearly as powerful and doesn't approach tier 1. The same goes for the slayer and abjurant champion. They're not nearly as powerful on a psychic warrior or hexblade respectively.
The only two things on that list I don't see a moderate level druid having an answer to is the skill challenges (for SOME skills) and the planar travel.