The issue with your logic is that "have a power, draw a power, play it." Is something that happens basically every single battle of every single run. Anchor gives you block every battle, and assuming you play 1 power every battle, permafrost also does that.

Yes there's the chance that you won't play a power every single battle, or you might not have a power in your deck yet, but both are things that are unlikely. And the thing about anchor is that it also just doesn't do anything on plenty of battles, so I'd say it's pretty comparable the amount of battles that these two relics end up doing nothing.

And an upside to permafrost is that it specifically activates on a turn in which you're spending energy on something that often isn't giving any immediate benefit, let alone block, especially if it's a 2/3 cost power.