Very likely playable in a spell-slinger deck (especially as you likely include the Adventure dragons in that deck), but otherwise a flat out 7/7 isn't worth it to jump through hoops for
Getting the effect in a different color is a big gain
The starting life totals feels like someone went, Forty is too much and twenty is too little, eh make it thirty. It turns out that thirty starting life actually feels right
Creeping Tar Pit Although Creeping Tar Pit comes into play tapped, it can be tapped for both blue and black mana
Relying on having dorks in play makes it narrower, less good early and more situational
Dark Confidant has also been a long time Plan B for combo decks, whether in the sideboard or the maindeck, such as Paulo Vitor Dama Da Rosas Dark Depths deck from Pro Tour Austin: Creatures (11) Lands (24) Spells (25) Dark Confidant is great for finding combo pieces and great when you dont assemble the combo