Unless you are a very experienced hiker, I recommend going with one of the groups that frequently organize these trips. Baiguate is a very good operation, and also Camping Tours. You want to avoid the mountain if it has been raining in the country, which is the case right now. The reason is that the roads become very muddy, making an already difficult route, treacherous. My impression is that one needs at least a week sans rain for the mud to dry out. That said, the people that do the trips, all the time, such as Baiguate, know what they will come across, so I would think they would be the ones to alert you as to when is a good or bad time to go.
The dates of 8, 9, 10 are for a fast-paced trip, but doable. When I went (in October), overnighted at La Cienega (after Manabao) and then got all the way up to the last camping ground -- the one where the government built a new site, at Valle de Lilis, way up from Comparticion -- in one day. It was a gruelsome tredge, but if you start out at 7am you will get to the Lilis site by daylight. Our camp leader wanted us to stay at the new site. From there, it is but a relatively easy one hour walk to get to the Pico Duarte. We did that the next day in the morning. Need to go early before the clouds set in. Then we spent that whole day at the Valle Lilis site, to return the next day. So it was one day to get there, one day to rest, and the next day back, about what Baiguate is proposing.
By the way, as to whether the effort was worth it? 200%. The excursion costs more than a stay at a luxury hotel, but it is a priceless tour. The Carpenter's song, "I'm On the Top of the World Looking Down on Creation..." kept ringing in my mind.