OK, I gathered a bit more data on gearing. It is noisy, often from 2-3 data points.
Speeds at 11500 RPM
4th 6th 8th
McLaren (ALO) 175 242 316
Mercedes (HAM) 186 256 322
Ferrari (VET) 180 248 320
Renault (HUL) 191 261 329
RedBull (RIC) 333
So McLaren is geared shorter. Specially quite a lot shorter than the other Renault teams. Interestingly, only a little bit shorter than Ferrari, which considering the power shortage suggests that the gearing is still within an acceptable range. I don't think Ferrari got it very wrong, and this difference can account for what, 1 tenth a lap?
But, Both Ferrari and Mercedes use a much higher effective rev band, often in the 10500-11750 range, compared to 10300-11500 for Alonso.
Renault seems to be in between, like 10400-11600, and no data for Red Bull. Are their peak powers in different places? They use different fuel suppliers to Renault, don't they?
McLaren is geared differently, significantly shorter, but not so much that the gears are causing their current place at the back of the grid, IMO. In fact, compared with Ferrari and Mercedes, considering their lower power and higher drag, they might be geared about perfect. The short gearing might be behind their utter inability to overtake, though, by costing extra top speed.