It's really sad, while fixing the biggest problems with it by fixing tidal surge's enemy holding capabilities, it really does seem like they took one of Hydroid's most iconic, and unique, abilities away.
Of all the things to reconsider, I really don't care how "strong" whatever they changed it to is. The real problems with it were because of Hydroid's overall lack of ability to finish and kill, which weren't inherently the puddle's fault. It was a strange adherence to his abilities dealing Impact and Magnetic, which the rework proposes to remove, so instead of doing the rework all at once... maybe do it in two batches?
Just leave undertow on for a test period with the changes in place, before giving him a power that feels like it was a forced Helminth overwrite?
Worst case, treat it like Grendel's ability if they're really deadset on the removal of "enemy denial", which really is, and was, and always will be, a problem with how the enemies are counted as still alive for the purposes of defense waves, which potentially remains an issue for so many other powers out there, even still. I would love if powers like Garuda's totem didn't hold up the timer. The game has become about killing crowds, holding 1-5 enemies over across waves really needs to not be such a big deal.