The only conceptual way where defenders aren't OP if is the cards it can be used to protect are weak/boring.
Therefor I just think it's poor design. Immunity on one card was a much better concept imo as said card would usually go into tall removal territory anyway whereas defenders are there to allow orders (Damiens' most notoriously) to go off and then they've done their job.
They felt like immunity, arachas queen, neutral leader abilities etc. limited design space and then they introduce defenders.
As far as Swim goes, he's made plenty of good points in the past but from his unique perspective as a streamer also some terrible ones (being pro create/RNG for the sake of amusement)
His decks have pretty much reflected his capriciousness where on one hand he comes up with cool concepts such as Ocvist handbuff and that charges thing he did in Homecoming but then he'll also play Imlerith Sabbath and unitless decks.
Overall his presence might do more good than harm but it's hard to say.