Planeswalker Deck PWs don't necessarily have to be more expensive than mainline version. Both Ajani's in Aether Revolt cost 6 iirc. Would make plenty of sense for Planeswalker deck Bolas to simply be a 7 drop with slightly less exciting abilities.
So for standard purposes in comparison to the most direct competition (transgress the mind)... arguably worse against mardu because the only things this hits that transgress doesn't are toolcraft, thraben, fatal push, ballista, and scrapheap, but it whiffs on Thalia, Depala, Pia, and Skysovereign. Better against 4c Saheeli, GB snakes, and Temur Tower. We will have to see if the exile clause on Transgress ends up being more important than before now that another heavily graveyard based set is coming out.