Nihilus inconsistent cooldowns

If he hits a buffed hero with his basic, both Drain Force and Annihilate cooldowns are reduced, which is different than a normal PC nihilus. This can make his cooldown reductions appear very random. So he can start his turn with drain force at 1, annihilate at 3, and on his first action hit a buffed hero with his basic (-1 on each special: df ready, annihilate @2). Then he gets to use Drain force immediately for his second action. If a hero is debuffed that'll reduce annhilate to 1,then once his turn is done it'll be reduced to 0 (ready to use next turn).
Before he takes his turn you must look at the number of buffed and debuffed heroes and his cooldowns, and work out if he'll be able to annihilate based on that. Rule of thumb, lots of buffed and debuffed heroes will cause him to annihilate often.