I don't think a DH should be penalized for not playing defense. As long as MLB has the DH role, players who are primarily DHs should be judged solely in that capacity. That goes for HOF voting as well.
In terms of offense only, Betts still tops JD, so I'm fine with Betts getting the nod over JD. However, if JD had better offensive numbers than Betts, I would have an issue with anyone not voting for JD simply because he doesn't play defense.
Also, I stil don't think it's all about WAR when you're talking about 'Most Valuable'. I think intangibles have to be factored in, which granted, is a difficult thing to do.