Is Metamorphosis supposed to be the crux of her kit, or is it merely to enable the rest of it?
I run a build that uses the augment mods Energy Transfer and Duality, the former putting in the majority of the work. I maintain Mend & Maim while switching forms constantly, accumulating damage for when I need a room-nuke. And I never use her 2 and 3 abilities.
I don't feel like I'm playing her correctly, and I don't think I want to.
I don't want to recast her 3 and 4 whenever I switch forms, simple as. So I have an augment for her 4, and I never use her 3, because they don't persist through forms for some reason.
It's not like I can't recast this ability every time I shift form, I only don't because it's annoying.
As for her 4, I find myself using Maim 99% of the time, only using Mend if I have an extremely low amount accumulated and I'm not getting health from anywhere else. If you're not using the augment, this just makes Mend more spammable at higher levels, but with the augment, Maim is the only option past a certain amount of accumulated damage.
Metamorphosis itself also doesn't let you cast abilities while shifting, which is a tiny bit annoying.
On the other hand, if this were all 'fixed', it would probably make Equinox significantly easier to play. She's otherwise really quite a simple warframe with simple patterns, it's her jank that makes her interesting. Maybe. I don't know.
Also please change how the HUD displays the accumulated damage. It shouldn't be hiding among the buffs, and it shouldn't disappear briefly while switching forms.