To be honest, I think the car performance is fine. It should be based off Bahrain and the teams like McLaren, Aston and Williams should be able to develop up the field with their cheaper upgrades. I'd maybe bump all three a little closer to the field but keep them the bottom three.
What needs changing really is a few of the drivers stats and the personnel boosts further reduced (looks like its 5/7/10 for each tier this year?).
If drivers like Vettel and Ricciardo had the right pace stat they would naturally be closer to the other teams. Norris is a good example. He has a very high pace stat so even though his car is slower hes still fighting the Alpine, Haas and Alpha cars. Vettel at around 88 or 89 and Ricciardo around 86 and probably Albon at 83 or 84 would be a better balance.