I made a post about some general changes needed. However even with 16% hit warlocks are still trash compared to mages in 40 mans.
Some of the primary reasons why warlocks are bad is because they fall behind on trash. Arcane explosion is better than hellfire with not nearly as many drawbacks + blink for mobility.
Also the first 3 warlocks you bring lose out on 1 global +dot potential per mob. You also need a 3rd warlock for shadow to be better than fire warlock, then you need a shadow priest (literally the worst dps spec in the game, same tier as retribution) to max out with shadow damage. But even with the shadow priest fire mages are still better on single target.