Oz is a combo card, nerfing the pp cost is a good way to kill a combo card. You cannot nerf a combo card by increasing it's pp cost, which is the same reason roach is never nerfed by it's pp cost. That would straight up kill the card.

And remember this is RUNE you're talking about. "Just delay the power turn" is HUGE for rune since it's always about maintaining efficient pp cost on curve. I don't see much use of her if she become 6pp honestly, that mean you can only play her at 7pp, part of why she's so good in dirt rune is because you can also use her to refill your hand AND cast 1pp spell.

Delaying 1 turn for hand refill is obviously bad. At turn 7 what spell do you want to use? Grand summoning? Does it still relevant at turn 7?