Obviously there is always the question as to whether the GFS (or euro) are overmixing, however, looking at the synoptic look, I don't think overmixing is a culprit here. Going verbatim, the synoptic look doesn't favor a deep southerly or southwesterly flow at the surface. We're kind of westerly through the troposphere. The Southeast ridge there extends well across the deep South into Texas, and may even connect with the west ridge. In this scenario, we're cut off from the true deep tropical flow.
I would suspect the best chance of 70+ dews in this regime would be dewpoint pooling ahead of any front as we shift winds out ahead of it.