Toxic Deluge does the job cheaper, In Garruks Wake does it better, and if you really want to get crazy, Blood on the Snow doubles as a reanimation spell
A five-drop planeswalker in Modern not Karn not Ugin is a tough sell
The best thing about Battle Screech is that you can make two tokens first, and if you already have a white creature on the battlefield, you can flash it back the same turn by tapping your newly created creatures
The difference in power level is astonishing considering they each cost the same amount of mana
Those themes never really worked together, but succeeded separately
All of this combines to having threats that do require some hoops to jump through to get in play, but are very likely to stick onto the board once you have jumped through them