Hmm. I don't know how "generally-considered" that is, or how valid such a consideration is even if a lot of people believe it, but it's not a basis for balance because even if high-Fort creatures currently outnumber high-Ref creatures, that number will not be reliable over time. Indeed, if a defense discrepency was consistently the case, it probably bears rebalancing itself.How about a more subtle change, such as making it target Fort instead of Ref? I think it's generally considered that attacks targeting Fort are "weaker" than those targeting Ref, and it also helps to reinforce the mechanical distinction between Invokers (most attacks target Fort but have extra effects) and Wizards (most attacks target Ref).
For Vanguard's Whatever, I'd consider just using a different method of damage allocation, like adding in an ability score other than Wisdom, or perhaps just use a big die for damage with no ability score mod tossed in.