How about Wild Shaping in Horrid animals? It is not mentioned in the handbook. Is it because it is somehow illegal? Or because it is simply not worth it?
It seems to me that taking a Horrid bat form is somehow competitive with a Desmodu Hunting bat given the justifications in the handbook. The Horrid bat has a shorter Blindsense range, flight speed and does not have Scent, but gains an extra 5 AC, an immunity to Acid, 1 more point of Dex bonus and 8 more points of Con bonus.

And maybe for offensive forms things get better, since the Druid has better HDs than the original animals and benefits better from the extra 1d6/ 4HD acid damage per primary attack than they do. How about that, am I missing something?