Hey now, Helminth fixes Ash and Nyx. Zephyr has a use as an easy to get and use tank frame for the roomier maps(open world, Jupiter, Corpus Ships) for newbies, particularly now that her 2 is a very poor man's Larva/Ensnare. Hydroid definitely needs some love though.
With respect to the issue of Nezha - He is a phenomenal tank and support frame that has great hard CC, can provide *group* and *objective* DR, and can remove status effects. Only thing the Chakram needs is the fully charged one doesn't seem to duplicate when you use the augment.