I think having two different words for epistemic and instrumental rationality would be a feature, not a bug. There's already plenty of overlap between the two (knowing truths is useful, and can easily be subsumed in a discussion of instrumental rationality), but since they do come into conflict sometimes, it would be very valuable to have a concise way to specify which kind of rationality we're talking about. This would also make our replacing 'rationality' with some other term have a function beyond euphemism treadmilling, which makes it easier to justify to the anti-PR crowd.

But I agree "effective" kind of falls flat. Is there an adjective/noun set derivable from "wins" that doesn't make us sound like Charlie Sheen? (It can be a protologism.)