CotW Contest #387: But do not forget: they came as three.

As for your questions, "dies to legacy World Spells" is pretty much the same argument as "dies to removal", but worse. At least most decks have a reason to run removal. In any format where the likes of Concordant Crossroads is legal, players will have much better options to put in their deck, including better options to run as counters to a World-meld (such as literally any other form of removal). I could make my own "Masterpiece" supertype that serves the same functional role as World but doesn't interact with old cards, and I could even make a few tweaks to the "Masterpiece Rule" where I think the World Rule could be improved on. However, I see no need to reinvent the wheel when World already does what I want, barring some fairly trivial edge cases (and in any case if my intent is to show that World could be used in a more interesting and satisfying way than how it was originally, throwing it out and starting over isn't the most auspicious way to begin).

As for Orsval, he's useless by design. He is, simply put, a key to a lock. His intended use case is to cast after Leonette is already on the board, to cast Painted Vale for 3 and a delay. Keeping him alive for a turn is the final hurdle to getting the enchantment out. Maybe that's not to your taste, but in the original, I judged that the meld was strong enough to justify one of the cards needed to make it being objectively bad, and in the new version I saw no reason to change it. He's not an actively detrimental card, just an inefficient use of mana for anything but getting the meld out. Which is right at the balance point where I wanted him to be.

And as an aside, the description "seven mana meld enchantment", while technically accurate, is a bit of a misrepresentation. There are few situations where I could see someone playing it outright at seven mana. The far more likely play would be to play knights on any or all of the first three turns, Leonnette on turn 4, and Orsval on turn 5, assuming both cards arrive on-tempo (or you're playing Commander), and no ramp. For one thing, players are going to want to hold something back for protecting Orsval, or at least give the impression that they are.