I like the augment and I like that you can just double-tap to resummon when Merulina is at any HP. The only things I currently dislike are:
The K-Drive noises whirring right inside my eardrums whenever Merulina catches up to me, please god mute the noises or put an option for it.
A short invuln when Merulina dies would be nice, like other abilities that do similar.
The sea snares are nice, but needing to basically stop for Merulina to fire them once again clashes with her passive.
I'm still of the opinion that this shouldn't need to be an augment, and should just be a default hold-ability for Merulina, but I digress. IMO she's always been good in a niche way, and this just makes it easier to use her without needing helminth investment.