July/August in Raja Ampat are typically windy with rain. You might luck out and get good weather, but better to choose a time more likely to have good weather.
For the diving in Raja Ampat it doesn't really seem to matter. Always good and water temperatures is always warm, visibility is always variable.
For best conditions weather-wise I always book my Raja Ampat charters in mid-October to mid-December. Seems to have least rain and hardly any wind. We usually get about 1/2 day of rain during an 11-14 day trip during that time period. I am always aboard for the trips and so I want to have the best chance of good weather and best diving.
I have been diving and taking small groups (always limited to 12) every year since '99. I've taken both land-based and ship charters and also in other months of the year. For 2011 and 2012 I've only booked charters in Oct/Nov.
If you must go in July/August, choose another area. Perhaps Komodo. For me it is not as good a trip as Raja Ampat, but a better option for those months.