The Sweepers Your sweepers wont kill your 0/4 and 0/5 creatures since they kill creatures based on their power
Joshua fits like a glove in Jeskai Oculus for this reason, playing a similar role to Tersa Lightshatter
Also note that this is a cast trigger, not an ETB one, so if you cast a creature and it's countered, you'll still draw a card
The obvious answer didn't take long, why not do both
My guess is that this came up in price a bit to over take some more notable cards like Dead-Eye Navigator because its great for Tribal decks, like Werewolves
Water Pokmon have some of the best support across any type, with access to multiple Energy accelerators, draw support, Energy recovery and search options