Diablo what? Supercorsa? or Corsa? Corsa3? Rosso or Rosso2?
Wow thats not a lot of miles.....i'd get over 2-2.5k from a Dragon Supercorsa sc2/1, sometimes over 3k but pushing the slickness haha, and they are used sc2/1 practice tyres, 4k from Diablo Corsa, and haven't yet used another Diablo I have, think it's a sport. Just fitted Diablo Supercorsa sc2&1 to one i4 bike so will see. Always Pirelli.
Most tyre types are apparently brilliant according to many riders, and you can't argue, as there are a mix of riders reporting such. If you are on carriageways all the time, and pushing on, you'll wreck a soft tyre anyway, but still, can;t explain 1500 miles unless high speed and hard motorways and pressure high perhaps.
Hope this next one goes further?